tl;dr on the meta plot: They basically killed cosmic horror for [gay] romance.
They spent years building up the void as containing an unknowable threat to all existence, eventually personified as the "Man in the Wall", kept in check by a Warframe pilot who trapped himself in his signature frame, Harrow... who will just randomly show up in your ship to taunt you ("Hey, kiddo.") after you complete the Chains of Harrow quest.
In the New War quest, the explanation of your void powers and certain characters' seeming immortality being from a literal deals with the devil you don't remember because of the nature of the deal was a nice twist.
And then, at the end of the quest, they reveal the "Man in the Wall" is literally just a talking wall. It's not describing the barrier between worlds, or an an allegory for an entity existing outside of normal time and space... no,
that's literally just how the entity physically appears.
In Kingdom of Duviri open world, they turned the void into a fantasy land based on a morality play by one of the architects of void travel acted out by action figures.
Then in the Whisper in the Walls main quest they make the climax of the story about unrequited gay romance between who is probably the most important character in the metaplot, Albrect Entrati, and his effeminate assistant, Loid. At least the talking fish, bird, and dog-thing won't die from void exposure now.
We can beat back the all consuming Indifference of the void with gay love. Great. Just fucking great, Rebecca, thanks for that excellent writing.
(A side note here, this is a similar play White Wolf did with the Aeon/Trinity + Aberrant + Adventure! table top RPG meta-plot. The Magneto expy set all the plot in motion because the Doc Savage/Professor X expy rebuffed his gay love... and you don't find this out till they release the third game and the writers confirm the subtext on RPG.net. Excellent bait and switch. Thanks for ruining it. Just a reminder that White Wolf TT RPGs has always been lame and gay, us 90's kids just didn't realize it at the time.)
No, what REALLY killed it for me, and finally made me quit, was the over-hyped dogshit Warframe 1999 expansion. Every character is unlikable. On first playthrough the story is incomprehensible. They
hype villains in that story and almost immediately kill them off/disappear them. Everybody dies, but they all come back because you're in a time loop. At best, the lore makes little sense; at worst it's a series of reveals that cheapen a decade-plus of world building.
AND FINALLY, they added in dating sim elements where you can romance your Warframes. Oh, wow, I can get a New Years Eve kiss cutscene with the proto-warframe of my choice once every month. Thank you, but no, I prefer to
spend New Year's Eve hugging Albrect Entrati's cat.
Oh, and apparently there's a boy band that's been turned into Infested that you can fight too. Don't know, I quit before they finished releasing that boss fight.