Earlier quoted context omitted.
For professional use, how does modern GIMP compare to modern PS?
And follow-up, why is it so hard (for volunteer contributors) to implement those missing features and functionality?
For example, Figma (non-open source) is doing stuff that myself as a designer, I find very subtly innovative for a browser-based graphics program. Sure, they are actual company which can devote more resources to the product, but I think it helps that some very talented designers are using it and thus, can give feedback and suggest new features with engineers to support the effort.
Similarly, I'm sure a lot of open source projects have thrived because the contributors are active users whose skillsets (coding) overlap with the project.