I had noticed almost no hostile mobs spawn in the overworld on java servers, and at first I dismissed it as just unfortunate rng... but then I came across this reddit post wherein other players are also noting hostile mobs are hard to come by in 1.17....
https://www.reddit.com/r/Minecraft/comments/nyplwd/minecraft_very_few_mob_spawning_117/

Edit to add: it appears the line with mob count is also missing from the f3 screen.