OG Doom is still a fantastic game that holds up better than many of the modern boomer shooters (nothing against them as I enjoy them too), and still has one of the best modding scenes in gaming that is more active than ever. People have made so many levels that surpass the originals in quality, there’s basically endless content there.

I’d recommend using the GZDoom engine (there’s a lot of others but that’s a good starting point), and for some mods that show off the cool stuff that can be done but are still accessible to newer players: The Golden Souls 2, Pirate Doom, Eviternity, and Ancient Aliens are some that are worth checking out.