COD4 was incredible, could change pretty much everything about it, custom maps, modes, models you name it (here's one I worked on back in the day https://www.moddb.com/mods/cod4-minigames).
I agree Roblox is a cesspit of overly monetized P2W experiences, and minecraft from what I've heard has most its audience on micro transaction (p2w) based servers.
As I mentioned in another comment, fingers crossed s&box can bring back the glory days. Although I worry there's now been a shift in how people play, and the "why" people build things (money, versus personal gratification / fun), similar to how the same thing has happened on Youtube (most people don't seem to create for the fun of it anymore, but rather to make money).