Between GIMP releases we saw entire graphics pipelines, conventions and workflows come and go. We had the Affinity suite, Canva, Paint.net, Clip Paint Studio, Sketch, various attempts from Adobe at expanding beyond the Photoshop ecosystem (Anyone remembers XD?), probably something else I’m missing right now. Now we’re in the age of Figma, with its own UI and quirks.
At this point it’s probably easier to accept that the GIMP UI is simply what GIMP developers want it to be.
True, it doesn’t make a lick of sense, but the same could be said about Turbotax, Jira, SAP… or God may have mercy on your soul, Avid Pro Tools.
It is what it is. It’s not like there are no alternatives anymore.