Open source projects are made and managed by software developers. Not by graphic designers, not by UI/UX experts. Developers will make something that works, that scratches their itch. But it can take years if not decades for a project to actually look polished, be easy for a casual computer user to use. For most open source projects, the way to contribute is "make a pull request", which usually involves more programming than a design person can or wants to contribute in order to make things look good. For a project to be user friendly, it needs people besides software developers working on it.

See, for example, Mastodon and Lemmy. They're excellent federated social media, they should replace Twitter and reddit. But I heard someone say the word "Federated" at a bar last night while describing them, and I pegged them instantly as a software developer. Federation? Choosing an instance? Casual users glaze over. Without a dead simple onboarding process, they will never replace corporate social media.

As a long time Ubuntu user, I get annoyed at the way they've moved towards kiddy proofing a number of things, but I can tell they're doing their best to make it usable by more casual computer users. It's still not 100% there, but it's way closer than it has been, and it's one of the most user friendly distros.

The public market consists of a wide variety of people. From computer experts, to grandmas who barely know what email is. Linux will never work for those grandma types, whereas closed source stuff like Mac OS does all those complicated things for you (but you have no control over). Grandmas like that, computer experts don't.

Now who do you think the public is mostly made up of? People who fall closer to computer experts or grandmas?