I feel like the implication is that people prevent you from customizing stuff for ego reasons, but isn't it a lot of code and testing to implement the personalization UI? But thinking about it more, I suppose the answer is to let the users write their own clients. Netflix should have a JSON API that's a list of all the programs, and each record should contain a link to video file. They don't do that because of DRM an…
"I suppose the answer is to let the users write their own clients" Have you tested that supposition against the percentage of users that can write software and compared it to the percentage of users that don't code for a living?
But also, maybe the problem is we often develop apps as a fragile monolith which is definitely not intended to be customized in terms of UI. When the core or your application is designed library-first so that your executable is only an opinionated wrapper (client) around the lib, you make it easier for others to reach their usecase by implementing a different wrapper. I don't see a reason this wouldn't apply to composable/reusable GUI components: early Mozilla (XUL) is a famous example of that.