Thinking back now, it’s probably nostalgia speaking, plus the fact that some of that soul still remains in the game in old tile sets or by replaying old content really. It is still somewhat enjoyable, since you can just engage in the gameplay more or less.
Old Warframe lore worked because it relied mostly on its cryptic worldbuilding, things were uncanny, weird and scary. At best you had your unreliable unknown narrator TM giving you orders to slay everyone around you or hateful genetic abominations shouting at you as you rushed through the dark hulls of their dreadnoughts, or the mystifying codex entries.
Everyone and everything was hostile to you. You are awaken as a biomechanical being by an unknown figure in the ruins of a long lost civilization and are met with a weird caste of would be humans with corrupted flesh trying to harness you who otherwise are alone in an unknown decrepit solar system that seem so strange and in a state of eternal war.
All the planets we know turned into nightmarish versions of themselves and any semblance of humanity is mutated and unrecognisable.
This used to be cool, even if without much substance. On top of that that we had mythological aesthetics, mostly Oriental but also Nordic, Celtic, Roman, represented in the score, design, weapons, Tenno culture and martial arts etc. All of that was lost or largely diluted into the whole lost traumatised space kids without identity.
But don’t get me wrong, I am not so much a purist, even after the Second Dream they consistently pumped good stuff aesthetics wise and while it wasn’t the ideal path in my opinion the game still had potential. Stuff like Cetus could be less of a slop but things such as the Orokin sentient tower made of flesh worshipped by forsaken central Asian remnants of mankind is a cool concept, though executed poorly, as an example.
But nowadays I don’t know what to make out of it, the multiverse trope is as generic as one can get and screams lack of creative direction.
TL;DR: Would prefer the game remained cryptic, badass and thematic, it didn't; But not all was lost, for a while, now it seems to be in a grim state.