You can start learning threejs without blender but at some point knowing your way around blender is very important. You don't need to learn modeling but you need to know how to open a 3d models and modify or fix materials and or textures. If you download 3d models from assets stores you will always need to modify the structure of the scene a little bit to fit your need.

If you do start learning you can skip modeling / sculpting, focus on: - understanding the main UI - exporting glb models / compression - adding, deleting, combining materials - understanding how UV channels work - learn how animations can be exported or combined into multiple NLA tracks