Sounds like, if you want a capable materials, mechanical, chemical and electrical engineer to write your pull requests, you'd need to pay them a salary they request. (Them in plural, because it is unlikely to find a single individual good at everything.)

Software people like to say that software engineers is super complex and difficult. On the other hand, an enthusiast occasionally makes great FOSS contribution by filing a pull request. For some reason, that is?[1] quite rare in many other forms of engineering. If it is only because of capital cost differences of building things in physical world vs building in software world (which affects stuff like learning by experimentation), maybe we should acknowledge they are a part of reason why building things in physical world is complex and difficult.

[1] Or looks rare, I may be mistaken.