I've been playing 1.21, and it's my first actual time playing with the 1.18 world gen, and I think I can say it kind of sucks. It feels as if normal caves don't exist anymore, and the new ore distribution means you have to constantly make trips back up to the surface if you run out of coal. The diamond generation is dumb as well as you can just enter one of the giant fuckoff caverns that are far too common, find sculk, then mine all the sculk up with a hoe and reveal a ton of diamonds because of the boost to spawning when not touching air, along with diamonds spawning in larger veins, then use the XP from sculk mining to get fortune 3 and then never run out of diamonds again.
The world gen is also too big, they brought back the biome independent terrain from beta, but beta used a different map for biome distribution, where as this new world gen uses a temperature map plus terrain details to drive biomes, and the noise is too billowy and large, so hills are giant yet too smooth to be interesting. Building in the giant terrain isn't as natural as it is with beta style terrain with its natural overhangs and crevices that are small enough you can actually do things, while still having flat surfaces, something that the 1.7 terrain had still from the old caves and biomes driving terrain, although you had to do a bit of exploring to find the better biomes.
Essentially I think Notch got the terrain perfect in beta, and every iteration since has just been missing the point of it. The new world gen feels over designed, like it was made for screenshots and like the mining experience was designed around a gameplay loop rather than just being part of the game. I wish I could go and tweak the world gen with a datapack and make the giant fuckoff caves a lot rarer, but I've already started playing the world so I can't really do that without restarting.
