Moving to client-side rendering via React means less server load spent generating boilerplate HTML over and over again.

If you have a captive audience, you can get away with making the product shittier because it's so difficult for anyone to move away from it - both from an engineering standpoint and from network effects.

It seems most of the complaints are about the reliability and infrastructure - which is very much often a direct result of lack of investment and development resources.

And then many UI changes people have been complaining about are related to things like copilot being forcibly integrated - which is very much in the "Microsoft expect to gain a profit by encouraging it's use" camp.

It's pretty rare companies make a UI because they want a bad UI, it's normally a second order thing from other priorities - such as promoting other services or encouraging more ad impressions or similar.