While we (Krita) don't have 3D support yet, but we do have perspective and other kinds of rulers (assistants) support. There are lots of other features too like wrap around mode for seamless tile creation etc.

You're absolutely correct, but you know how these things go: people look up FOSS Photoshop (or more likely "free photoshop alternative") on a search engine and GIMP is the first hit and when the tools for drawing aren't as sophisticated, users will say "GIMP sux" because it doesn't match their expectations if they're a drawer even if it's a perfectly adequate image processor.