I’ve never heard anyone say Windows is a problem because it’s proprietary. I have heard that having to pay to upgrade is a pain because you (the company) have to budget for it. Even then, you would also need to budget for the downtime and time to verify that it works before deploying the update, and both those have to be done on Linux too (it’s why LTS releases are a thing).

Anyways, Windows 10 may have its problems, but Microsoft the company is doing pretty well. Their stock is up about 50% this year (200% over the past 5). And that’s not to mention the fact that they’ve open sourced .NET among many other things.