Another part of the trouble is that Blender suffers from some common ailments in the FOSS world, notably a lack of UI refinement, stability, and documentation. While there are people trying to improve these things, and over time they are making some decent progress, and it's not as if the Autodesk products themselves are perfect on any of these counts, on balance there is still a much stronger ecosystem around the incumbents. A challenger like Blender needs to be not just playing catch-up but dramatically in the lead to shift this sort of market.