Firstly -as many others had pointed out-, you really should work on your formatting, spelling, and grammar, it makes what you write not as fun to read. (and indeed it helps stave off the vulgar side of your peers when they make dismissive one-liners about it)
And secontdly, Apologies for any offense.
--About content being repetitive
I think you should be more honest with yourself here; Warframe was always repetitive, it's just something about the current circumstance is causing you to be bothered by it now -indeed I feel it too-, maybe it's the convergence of disappointment -from the tennocon deceptions- and the game's overall lack of difficulty, which gives the game a "chore-like" quality to it.
While I agree there are things that are locked off to people with better stuff, -eidolons, arbitrations, orb mothers, lichs, 8-player missions (ditched)- I think what is craved is a kind of dungeon-esque difficulty barriers where you must get better (or have better gear) to progress to unlock some new area -something warframe lacks-. Instead what we have in the form of "difficulty" is doing the end-game tasks well and speedily. Doing an eidolon 5X3 is better than a 2X3, doing arbitrations up to 1 hour is better than doing it to 20 minutes, doing profit taker in 3 minutes is better than 15 minutes. Due to this, there is no sense of "discovery" or "accomplishment" (although improvements could be seen as accomplishment), instead we have efficiency, "lootiness", which leads to tedium.
--Warframe as a winning simulator
I spose part of your grievance is that since everything is turning into tedium -lets be honest, most MMOs are like this- Warframe has another problem with difficulty -Overpowered warframe abilities-, Gara can give a player a 90% Damage reduction, Octavia can make her entire team invisible which can be combod with banshee for silence and damage boosts, Grendel can devour 10 enemies, spit them out, and then magus lockdown, ETC.
While I'm sure there are other factors at play, the ridiculous abilities available to us -curiously- further take away from a sense of "skill", instead turning it into team compisition and technique, indeed have you tried to do Ambulas without CC abilities? Tried doing eidolon fights without the Volt-Chroma-Harrow-Trinity combo?
Indeed it almost feels that DE has long since "Game-Deved" themselves into this hole, and they seem ???to balance the enemies around the OP warframe abilities???
---About Grind reductions
This is the part where I think you aught to reconsider your personal narratives, DE has actually reduced the grind ALOT, even if they backpedaled a bit (with the 21 arcanes thing); Do you remember how arcanes USED to be gotten? (in 8-man raids that took 40 minutes and only gave one arcane), Do you remember how bad bounties used to be paid out (ok, maybe it was too much)? Do you remember how the quill arcanes used to require farming mats for their construction? Do you remember fusion cores way back? Do you remember how focus USED to be gotten? (only through EXP).
I really think it's that since we don't have anything to strive for, -since DE kinda repeatedly trivializes it's own end-game- we feel a tad meaningless with our grind. Subjectively we're worse off, Objectively we MUCH better off, and I think a round of remembrances (I like that phrase) is in order here.
---About "grand coop"
"Grand coop" Coop outside of your squad (like clan leaderboards, the ignis wraith blueprint event, or scarlet spear's flotillas)
I get your sense that the game often feels a tad meaningless, just you in your squad, and you in your clan that you hardly speak to, no greater identity (like making clan NO.1, or helping Flotilla) no outer goals, just grind.
But even then, what would this entail in terms of gameplay?
--We had fairly non-invasive events before.
Hostile Mergers, Where you could help prop up your clan so it got a few more decorations it could place.
The Grativus Dillemma, Where players could shift the course of an invasion and determine the rewards for others.
Back when the first clan-weapons were introduced, and the Prova (the corpus electrical stick) Was a big deal.
--We also had some in-built clan systems
The objectionable Hema/Mutagen Sample grind for the various weapons.
The Dojo and it's clan weapons
The Drydock (I choose to count this separately)
--But I think the fact that you (and many others) passively discounted this suggests that there is something lacking, some kind of engagement.
---Solar rails and "Grand coop"
This -I think- would had been a solution to your grievances here, a kind of PVE-PVP game mode where you can engage a kind of "mission node geopolitics" gameplay that indeed -felt like fighting/grinding for-. Indeed I feel this was the LAST time we had some kind of meaningful "Grand Coop", where clans could "fight" each other over taxation rights over profitable nodes, I remember how that went, somehow a much of jerks managed to achieve 100% taxation rate of the best nodes and managed to piss everyone off.
-To be a bit personal.
I remember how this one clan "eastern kingdoms"? which had a 0% tax rate -and thus adored- were taken of of that and turned into a 50%? tax rate by another clan, which was later changed (either due to conflict or internal management shifts) to a 100% tax rate. (I also suspect the solar rail system may have encouraged some DDOS attacks on DE to lock out certain clans at certain times.
---The Scarlet Spear
While I don't really "like" the scarlet spear, I think it deserves a note since it tries to do something unique, while it isn't a "indirect PVP" event -like the Grativus dilemma among so many others- it instead tries to create a "grand PVE" situation by instead encouraging "grand coop" by getting people into team roles, with the division of space and ground, but also with the time-limit -to hit the 100/100 limit-. Indeed it's a kind of event that -in addition to grinding- takes some planning on the part of the participants; Do I want to do the ground or space? Whach flotillas should I commit to? Is it even a good time to start since the 100/100 time limit is so low?
There is also a quasi-dysfunctional thing people on the float can do, -heal other squad's beacons- for 75,000 credits, (Instead it should lower enemy level) that is a step towards this "grandness", but still.
This all suggest they're trying to further interconnect the game -to give your grind a meaning- but they're doing in clumsily.
---Difficulty scaling with mastery ranks?
I guess?, I still want to have this achievement/task oriented difficulty system which unlocks more grind systems/difficulty.