I'm not entirely fond of Warframe's challenge factor being centered around enemies and random obstacles becoming increasingly more durable and dealing increasingly more damage. It leaves something to be desired in terms of interactive gameplay systems, as everything can be gunned and meleed through, and abilities are easily spammable.
Maybe that was the intent, but I can't help but feel as though Warframe could be a power fantasy while also requiring a bit more skill on the players' part.
Let's take a look at the game modes.
Extermination, while as simple as a task as killing everything there, I feel like there could be some sort of dynamic system that'd spawn harder enemies the more you kill. The enemies are also usually spread extremely far apart, so the individual enemy is never a threat. The amount is also pretty low, and so more enemy density as well as enemies with interactive mechanics in order to disable and defeat them (along with more minibosses in the style of the Bursa and Nox) would be very welcome.
While on the topic of enemies, Nullifiers and Energy Leeches are terribly designed enemies. Having an enemy being able to just exist, walk relatively nearby and instantly cancel any ability you had running is annoying and makes frames like Limbo nearly obsolete on Corpus missions, as the main portion of their ability synergies comes from a large radial bubble that can can canceled out instantly. Energy Leeches, on the other hand insidiously drain your energy without any refund once they are killed. This promotes using Zenurik's Energizing Dash on way too many setups, because energy in this game is not reliable in drop form and can be taken away very quickly. These two enemies destroy Frames who rely on their abilities to survive, forcing players to take easy alternatives.
The rest of the enemies themselves don't really have any distinctive way to deal with them the most effectively while also being somewhat challenging other than by just shooting them in the face. I feel as though Snipers and basic grunts should have some distinction between how I deal with them. I feel like I should want to constantly dodge out of the way of Sniper aim lasers to avoid taking critical damage while also being weary of the fast approaching melee attackers.
Spy missions are very boring, as the vaults are extremely easy to break into (thanks ciphers for not helping the problem at all). Their set up is also very easy to understand, and the obstacles are extremely basic, while the enemies are sparse. You'd think the highly important, top secret data would have more than 5 basic Crewmen defending it with a couple of lasers. Spy missions should definitely not be easily completed with ciphers, and the lasers should be more strategically placed, with better enemy placements, who are also tougher and more numerous. The puzzles could also suffer to be a bit more challenging, akin to Lua's.
Sabotage consists of running into mission, shooting thing/hacking thing, maybe waiting, then leaving. A much more complex multi-step plan would be much more engaging, with increasingly difficult enemies as you fulfill more objectives.
Mobile defense should actually be mobile, and not defense points. Defend a target that moves throughout a mission.
Capture is definitely the most egregious of offenders, as it consists of running into a mission, one-shotting a random enemy, and leaving. Enemies should try to actively defend the target while they escape. perhaps leaving behind environmental hazards and locking down the doors to buy themselves extra time.
Pretty much all of the game modes are so extremely basic and antiquated, and they really feel like they came from 2013. The enemies aren't any better, with the catch-all solution being to just shoot it. Warframe can be a power fantasy, but I feel as though it should also have some dynamic and interesting gameplay, with better enemies that will encourage more skilled play and keep players more engaged. Antiquated enemy and mission design needs to go, and more challenging gameplay in. Steel Path just isn't cutting it.