For those who use Blender for work, how far are models like Astra away from using Blender to create something good enough at a junior, senior level?

I don't know a about Blender, but frontier models already do a good job generating scenes in Three.js:

https://threejseval.com/

Blender can be guided with Opus 5.5 to do reasonably detailed buildings and generate textures, and modify existing models, say a car, and add doors. There is still a lot of handholding, but it's good enough!

Fable 5.2 is really good at using Blender from my testing. That being said, even smaller models are good enough for junior level work, it just depends on what deliverable or metric you are looking at. Most agentic LLMs can now do low poly assets for example.

More skilled technology users get better results when asking LLMs to do technology things.