I don't know how materials work in Asset Forge, but they have a guide on their site for exporting models to animate with Mixamo: https://kenney.nl/knowledge-base/asset-forge/rigging-a-character-using-mixamo. You could also animate things like moving platforms or doors in-engine with an AnimationPlayer.
Speaking of Asset Forge, Kenny Shape is a similar thing for quickly throwing assets together. It has a really fast 2D workflow for creating 3D models that reminds me of Doom mapping a little bit. For lo-fi levels, you might also like Crocotile 3D or the combo of TrenchBroom + Qodot. Crocotile is great for repurposing 2D pixel art tilesets from itch or OpenGameArt into 3D assets, and Trenchbroom/Qodot is a more fully featured level editor I've seen people work crazy fast in.
Late response but cool song recommendation :)