Ok, I'm probably one of those people who called it sterile

But I also like AoA's over the top character theme, which a lot of people hate. So everyone has their different tastes
I don't think BLT lacks theming per se, I think it's more that the theme is modern/sleek/minimalist. So, for me, when I compare it to VWL, AKL, BWV, Poly, etc... those have a lot more character and make me feel like when I leave the parks, I have a totally different vacation that I'm coming back to, and feels very different from most other non-WDW hotels. BLT feels a bit more like the standard convention hotel (to me at least).
Non-theming related, one of the things I dislike about BLT is how big it feels and how disconnected it is from the main building. Some of this may be that I don't know my way around compared to other resorts, so I've gotten lost a few times

I admit, I've gotten lost in BWV before too!
As someone else mentioned, I do like that BLT has Mickey artwork, and other hidden Mickeys. Having just come back from a stay at the
Disneyland Hotel, if I were to redo/add to the BLT theme, I would make it filled with hidden Mickeys and tributes to classic WDW/Walt. However, a lot of the amazing touches in the DL Hotel they obviously wouldn't put into a
DVC unit--Mickey shaped faucet handles, hidden Mickey lamps, the incredibly magical headboard

But I think they could still add some classic Disney/Mickey touches in BLT to give it a bit more character.
Now that I'm looking at adding my MK-area resort, I'm leaning towards Poly, but funny enough I'm considering BLT too. I agree with you, the views of the MK area, even if you don't have a theme park view, really make you feel like you're on a Disney vacation.