There's a whole new wave of retro FPS shooters that you might enjoy. Heck, we might even be on the third wave or so of them now (they started to come back ~2010). 'Boomer shooter' is the term to search for: https://www.inverse.com/gaming/boomer-shooter-definition-ori...
Also check out advanced gzdoom mods. The gzdoom engine never stopped innovating and now supports near full 3D environments with slopes, room over room, dynamic lighting, etc. but still has the same core frenetic and fast gameplay of the core engine. Here's a good taste of what's out there: https://www.youtube.com/watch?v=O2Db5O5-xk0
Also check out advanced gzdoom mods. The gzdoom engine never stopped innovating and now supports near full 3D environments with slopes, room over room, dynamic lighting, etc. but still has the same core frenetic and fast gameplay of the core engine. Here's a good taste of what's out there: https://www.youtube.com/watch?v=O2Db5O5-xk0