Not to mention the common principles in most free software around interoperability and loose coupling. Apple and Microsoft (and the rest) have less to do on this, because they don't have to make their software nearly as generic. Microsoft famously fixed something in SimCity at the OS level. Google and Facebook don't have to worry about interoperability, which undoubtedly removes a lot of complexity for them. In some ways, free software has a greater burden to carry.
The problem with usability in free software is not one of culture or cooperation, it is one of capital. The fact is, Apple and Microsoft have at this point invested hundreds of billions in finding the best engineers and designers around the world and paying them to focus on polishing their operating system. By comparison, Debian's (very impressive) 3500 or so developers, maintainers, and contributors, are almost exclusively volunteers and working at most part time on their chosen packages.
If you want to see better free software, what I'd suggest to you and everyone else is this:
Next time you want to buy a phone, pick something cheaper, and donate the difference to a developer of free software. If you're an iPhone user and you switch to a Fairphone 5, say, you can throw £600 at someone like Joey Hess, or just pick an organisation that makes good stuff and give it to them if you don't want to find a specific author. Let's remind ourselves that if 1000 people did this, it'd be £600k of funding to improve free software.
Personally, I'd recommend a donation to the NLNet foundation: https://nlnet.nl/
(plug for nlnet, they're currently taking proposals and will fund successful ones: https://nlnet.nl/news/2023/20230801-call.html )