You could make the case that almost all the games of today are made with the tools Carmack and Romero forged back in 1994. We live in a post-Doom world, and even a wildly different game like the Sekiro: Shadows Die Twice owes a lot of its basic assumptions about level design and 3D space to Doom.
You could also, of course, just literally make a ninja game in Doom (or the open-source GZDoom, to be more specific,) which is just what modder Edy Pagaza has set out to do with Doom Shinobi, turning the classic FPS into a third-person action game complete with katanas, throwing stars, and wall running.
It's an extremely impressive conversion, and looks like a fun time. The current release lets you play all the way through Doom's initial campaign with the Shinobi arsenal, but Pagaza's end goal is a full custom map pack built around the new gameplay. You can follow Doom Shinobi on ModDB or the creator's Twitter or Patreon.
In addition to Pagaza's own audacity and creativity, I think the project really speaks to the talent of Doom's original level designers—that their FPS maps can be turned into 3d action game levels with entirely new movement options without missing a beat.
Modders have done some incredible things with Doom over the years. I've been following the FEAR-inspired cyberpunk shooter conversion of Doom, Selaco, for some time, and Doomworld's catalog of the best WADs of all time is a great resource for the intrepid player looking to dive into the world of fan-made Doom. Doom Eternal is fine, but we must never forget the simple fact that Doom is eternal.
