Why do the bosses/raids in this game feel so lifeless?

[Edax]

I havent played FFXIII, so I cant say anything about that - but it also kinda doesnt matter, since this isnt about FFXIII but rather FFXIV.

And in regards to the bossfights, I can only offer you my approach, which is to ask "Why am I here in this place?" and then look how the enemies, including the bosses fit into it - there are dungeons like Tam Tara HM or Hullbreaker HM where the fights have clearly been set up for you specifically.
But most of the time we're entering dungeons or caves or simply areas that no "human" has entered in a long time, so wildlife took over - and as long as the wildlife fits the general area you're fighting it because its in your way. Or you're in its living room. If you're asking yourself "Why am I fighting this Gobbue in WP?", you might aswell ask why you fought the group of those weird fish before entering the bossroom. I dont know, maybe you're doing that! Personally I'm fine with some bosses not having a whole bunch of lore or "story reason" beside "This creature lives here, its there home and all it wants is for you to be gone". Thats making them less "exiting" than bosses with a story attached - at least to me - but they dont feel out of place. After all, I fought a pelican outside of Brayflox Longstop so it would stop attacking me - why wouldnt there be a pelican in that area, 50 meters away?

...in regards to the plants: I phrased that badly, because yes, real carnivorous plants dont gain energy from their prey - btu who says that the ones in Eorzea dont? Real carnivorous plants also dont move around on 4 little legs that much - or at least not that I know off.

To put it succinctly, fighting the environment is the lowest level of player engagement. To use the opposite example, The Vault has some very memorable bosses because they actually are involved with the HW story, you understand their motivations, their faction and their cause, and their powers are actively talked about in the MSQ as a key plotpoint. Not only that, but the Vault is inside a landmark that can be seen from multiple zones, so it feels like your in a real place that actually sees regular use, rather than an instance that feels like it only exists in hammerspace.