Not killed exactly, but I hate what they've done to Minecraft. It used to be something kind of unique, a game experience that was universal among kids. They paid $1.6B to gate it behind a microsoft.com account and force schoolkids and school districts in to the MS ecosystem.
Plus the mob votes - stupid nonsense idea. You're the game devs, dev the game. Don't ask an easily influenced bunch of people (hello glow squid) for their opinions. (I will concede that Caves & Cliffs is finally going in the right direction but the Java client still sucks re: optimisation and it'd be nice if they put some effort into that instead of the PR puffs of mob votes, etc.)
If they could implement some of the low hanging fruit that would be a fantastic step but Mojang seemingly have zero desire to seriously tackle performance.