This needs to stop

[cyntreau]

Everyone has seen it multiple times at this point. An easy lith fissure appears, so naturally everyone equips a wukong/bramma or a thermal sunder titania and erases everything and gathers all 10 void stacks within 2 minutes and are sitting at extract triggering the countdown BEFORE THE REST OF THE TEAM HAS EVEN LOADED IN. This has existed since void missions were a thing and I'm SICK of the game NOT LOADING THE TEAM IN PROPERLY BEFORE THE MISSION BEGINS... I've never understood why the developers of a coop game can't understand why everyone needs to be in the actual game before objectives are completed... the networking/connection needs to be changed because it's actually depressing to watch level 10's miss out on void rewards because the host stubbornly sat in extract refusing to wait for everyone to have enough to get the relic rewards and people are getting salty about it in chat. This is a classic example of DE allowing players to harm other players experience and it's downright rude to have something like this exist ingame. Let me explain something to the devs since they clearly don't understand- there are many, many, MANY players out there (especially in free games) that DO. NOT. CARE. ABOUT. THE. TEAM., they will not cooperate at all to help other players, thus game limitations and rules must take this into account, for example, relying on the kindness of hosts to wait until everyone has full 10/10 void fissures to actually get their reward- many players could care less and the poor player that joined late literally gets NOTHING. This is in the face of THE SAME GAME that blatantly charges 70$ ripoff prime access bundles.. seriously guys, you need an actually good coop connection experience before you can charge for big league stuff like that.

[Hobie-wan]

I agree. People need to make thread titles that actually indicate what the thread is about.

[Markov]

One client loads (generally due to having a potato PC or old-gen console) and the other three are at extraction with 10 reactant before they're actually in the mission. Yes, the other three players could wait ~2-3 minutes for that person to scramble around trying to find the reactant. But that's wasting three players' time as opposed to one, and in the time spent waiting they could run another relic. 

Your proposed solution of not starting the mission until all players are loaded isn't great either, since for the other players that's essentially adding 20-25s to each run, which is a significant amount considering the runs can be as fast as 60-90s if everyone's actually getting reactant, completing the mission objective, and heading to extract in a timely manner.

Some better solutions to this problem:
 

1. Find a premade squad to do non-endless relics with; even if you load late, you start loading with everyone else, so you won't end up loading after 20-30s+ of the mission actually starting, and not be so far behind on collecting reactant and getting to extract.
2. Find a premade squad to do endless relics with, so that that load times are even less of a factor.
3. Lower graphics settings to put less load on your PC (this is generally only necessary if you're GPU bottlenecked, but it can't hurt).
4. Get a SATA SSD for your xbox/playstation to improve load times if you're on old-gen PS/XBOX (these are extremely affordable). If on Switch...not much that can be done. The console's hardware is just too weak to realistically compete with other platforms (aside from the original PS4 model with HDD, perhaps).
5. If on PC, do various optimisations like updating drivers, checking for and getting rid of malware, again make sure to have Warframe on an SSD, be sure that TRIM is enabled for the SSD, keept at least ~15-20% spare space on your SSD and enable over-provisioning if your model/software allows for it use dual-channel RAM with XMP enabled in BIOS, set power plan to "Ultimate Performance,"  close unnecessary programs while the game is running, play on a lower resolution (or use dynamic resolution) if you're GPU bottlenecked, be sure that Shader Cache Size is set to unlimited, keep drivers updated (and if a driver causes issues, roll it back to an older known working version), set a static IP for your PC to set up port forwarding correctly (applies for console as well, just is a bit more of a hassle), try both DX11 and DX12 to see which gives better performance, regularly verify/optimise Download Cache (especially after updates/hotfixes), restart the game every 2-3 hours or so to avoid memory leaks, check CPU/GPU temps to see if you're having thermal throttling, ...
6. If no amount of optimisations suggested in step 4 are able to fix your load times, try reinstalling Warframe, and if necessary doing a fresh install of Windows (I recommend Windows 10, Win11 still has issues and personally butchers my performance). If this does not help, then depending on your specs upgrading a component or two (CPU generally most important for FPS, SSD for load times, GPU usually not an issue unless you're playing on a high resolution that is too much for the GPU to handle (dynamic resolution can help here) may help. 
7. If the PC is truly so much of a potato (say, 7+ years old) that nothing helps with performance, put it in your budget to build a new one (reusing as many parts as you can, of course). Warframe performance has steadily gotten worse over the years gaming PCs don't last forever, if you're wanting to play modern games without it being a slideshow.
   
   I hope that at least some of the above suggestions, based on my >5000 hours playing this game and decades of experience with computer hardware and software, are beneficial. I had slow load times and low fps myself, even with decent PC specs, before implementing some of these measures (amongst others) - and I wasn't aware of some of the reasons until other people pointed them out to me.
   
   TLDR: The game is not perfect, but complaining about other people is not going to help. Be proactive in finding ways to overcome the difficulties you are experiencing. Relying on other players to inconvenience themselves for your benefit, or blaming the developers for not proritising fixing your particular complaint is a fool's errand. This isn't directed specifically to @cyntreau by the way, but to people who get salty because other people aren't playing an online game the way they want them to, or because the developers' priorities don't align with their own.
   
   As a final note, you are always welcome to play solo (or with friends) and avoid these types of issues altogether.

[Nekomian]

@cyntreau I'd follow some of Markov's suggestions, namely ones about putting the game on any faster available drive since long load times are generally fetching data from disk to RAM is taking a while.

The way most star chart missions are structured, joins are enabled to hosts until a certain point (usually mission is near completion or completed); forcing all players to have a full squad before the mission begins doesn't work / breaks the flow of gameplay, and making it so all remaining players have to wait for someone on a potato PC to load in to either begin or end the mission is also not ideal. The current system they have in place works for most people, who will likely have load times around 10 - 15s (mine on a pcie 3.0 NVME SSD are about 5s or so for most content).

They could adjust thresholds for join times to hosts for certain missions, but I've not had the situation you described occur to me in a long while and it limits matchmaking quite a bit if they made it so like as soon as you get a void reactant or two people can no longer join.

To clarify as well, this issue happens regardless of join times too; I've been in a few missions where people will not wait for a newer player to get all their reactant and will extract. Honestly, I think they should go the same route as they did with railjack void storms - have shared traces; the old system is a bit antiquated and has this issue of independent counters in a shared common mission, where you can contribute and still not get a reward because you didn't go to a specific spot where all the traces were. That said, it's more of an issue for newer players I've noticed, since after quite a few void fissures most people prioritize getting reactant to 10 before the reward period with no issue.

[Saear]

I agree this is a terrible mechanic. I've seen it cause other problem but most noticeable in short missions that players tend to speed run. Load times are not simple your PC ability to load the level. If you leave the stats box on during loading you can see when the level has finished loading. Sometimes you'll still just sit there at loading. I think this has to do with your connection/ping to the host pc waiting for information. This is a core design of Warframe, using a single players PC to essentially host the mission for the other 3 players.

As Naroxas said, the only real solution I've ever heard is to make traces shared as they are in Railjack.