If you parent with autoweights, you’ll see a small error message, “failed to find solution for one or more bones”. That means, autoweights didn’t take.
The first thing to do is to check normals and fix non-manifold areas of the mesh. You have issues with both. Enable “face orientation” in overlays to see your normal problems. Use “select non manifold” operation to find non manifold places so that you can fix them. Your mesh is too dense for me to enjoy figuring it out myself, but it looks like you’ve had some problems with doubled verts that got merged in some places but not others. That’s bad.
(Another source of autoweights problems is model scale. I like to make my models about 10-20 Blender units tall. It’s dumb, but it affects autoweights. 6 units tall may be pushing it. The “recommended” scale, with a character under 2 units, is terrible for autoweights.)
Note that autoweights don’t work well on multiple, disconnected meshes, like you have here. So even if you get autoweights working, it might be work how you want. Your best bet is to weight manually.
For your purposes, as a drawing reference, you might consider separating the object by loose parts (p->by loose parts in edit mode) and then parenting each object bone-relative (select object, shift select armature, enter pose mode, select appropriate bone, ctrl p -> bone relative.) At least, for some of the objects-- the spine wouldn’t be great for that.