this topics comes up almost monthly now but it's 100% normal and okay to reference 3d models.
some folks will straight up put 3d models in their comic which in that case the okayness kind of varies but usually if it's a free to use asset, paid for, or self made then it's pretty much fine. webcomics are a lot of labor so using tools to make things easier is normal and despite popular beliefs actually recommended.
Some folks are capable of drawing things 100% on their own but that's because of tremendous amounts of time spent studying, practicing and improving that skill but it's also not without referencing.
Personally I don't really care if someone uses 3d backgrounds or other elements so long as it fits with the style. and that's specifically referring to the elements being mixed into the art not those standard, comes with the program, has zero editing done comics that used 3d models for everything (that's another rabbit hole in a can of worms)
but yeah 3d backgrounds are okay so long as it fits well with the rest of the art otherwise you risk killing the immersion in your story