If we’re sticking strictly to free, I’m not sure Doom mods work if you only have the free version installed. Either way, people basically never stopped making wads since the game came out, and I try various ones out from time to time.

There are tons of them, so if you’re interested you can see what won the annual Cacowards throughout the years and start there.

https://doomwiki.org/wiki/Cacowards