First of all, DOOM isn’t raycasted. Second of all it’s 3D in the sense that all objects have xyz coordinates and can move in that space. You can miss the monsters by having a rocket go over their heads. The main limitation is that the levels couldn’t have more than one ‘room’ per vertical space.

The rendering can still be implemented as polygons (making it true 3D rendering) whilst still maintaining the same level-based limitations, as we can see with DOOM 64.

Doom is definitely raycasted. John Carmack was on the Lex Fridman podcast a few years back and talked about the Doom implementation coming off of Wolfenstein 3D: https://www.youtube.com/watch?v=I845O57ZSy4

Yes, Doom renders walls in a way that is broadly similar to to how contemporary GPUs work. Doom sorts the walls in view space via the BSP tree, transforms them to screen space, breaks them into non-overlapping spans of screen columns, and then fills each column’s pixels with the wall’s textures. The floor and the sky are not geometry.

It is 2.5D in the sense that no plane may overlay any other plane.

Please dont redefine what 3D means to a forum of smart developers