The UHC community is dying. No new gamemodes/scenarios for both reddits and hypixels uhc. Massive cheater problem in both. X-ray is (if you use it smartly) almost undetectable, also other closet-cheating problems.
Gameplay is annoying af. From someone who plays UHC for almost 5 years now, it is grindy as hell. Sometimes you mine for 20 minutes, find nothing, and get insta killed by a full diamond. Or you kill someone, and you get cleaned immediately, and that is not to bad in a short game like skywars, but in UHC you may have wasted just 40 minutes of mining, and trying to chase someone, just to be cleaned after 1 kill.
Lucky buck and op stuff I don't really see what you mean. Maybe a higher diamond spawn rate, but idk.
Lastly, bedrock doesn't have a massive pvp playerbase (unlike java, were even if the gamemode is dead, you still have 80 player fills).