I feel like this has only really been the case since about 2015, so instead of ascribing it to a "jack of all trades" philosophy I believe it can be more readily explained by a "lets hire a bunch of webdevs to work on our desktop OS" philosophy.
I don’t think it’s a coincidence that quality plummeted afterwards.
[0] https://arstechnica.com/information-technology/2014/08/how-m...