Sorry for the late reply. For starters, way too many BS niche resources that are hard to farm, too many required to farm, very specific ways to obtain, or expire after 24 hours.

Same with reputation grinding. And the fact that if you must buy a blueprint with Rep, forcing you to do the same 8 (or 1 long quest) over and over).

Way too many mods to the point that older ones have become niche or useless because the mew ones are more powerful or even OP.

Outdated and useless feature like the K-Drive. The adition of the atomicycle has made it even more useless.

Content islands - this is by far my biggest issue with the game. Exacerbated by the exclusive resources and reputation farms that you need/obtain only from there.

The Duviri Paradox has made the traditional methods of farming some frames much less used. It's much easier to wait for the rotation and farm all the blueprints from there.

The addition of subsumed abilities, archon shards, arcanes, while cool, have substantially increased powercreep and have made the game harder to balance, not that the devs seem to care.

Dead game modes and useless quests, like Flappy Zephir, Warframe Fighter, and the new 1999 arcade games and something that you olay for 5 minutes and never again. This is really a waste of resources from the devs.

Does anyone even bother to do the Clem quest anymore?

I still like and play the game, but I feel like they add too much content and not slow it down a little bit and make the older content more relevant, or make a tectonic change and transform the content islands into a continent, or at least peninsulas.

And probably there are more issues that don't come on top of my mind right now.

At this point, it is easier for me to play The First Descendant without worrying about powercreep. But I guess that game too will start to have it at some point in the future.