Holy hell, a lot of what you just described hit right home with me.

I started off as one of the cheap developers ("technical consultant") for one of those Microsoft business products. Almost every single one of our customers are already ingrained into Microsoft ecosystems and setting up the system we customize and sell is mostly a matter of integrating into their existing AD, Exchange Mail Server and sometimes their private cloud. I was pretty ignorant of open source tools that would tremendously help even if you're mostly using Microsoft. Ignorant might not be the right word. It would be more correct to say "afraid to peek out of the comfortable Microsoft bubble". It wasn't just me, a lot of propriety consultants don't really bother with anything else. If something's beyond our capabilities we can always get the support of Microsoft, supposedly. This chain of responsibility give end customers assurance somehow. Like you said, assurance on who to blame and sue at least.

Took me a while to break out of Microsoft bubble and now I do open source ERP. I do get by okay, but I think it's mostly because my country cannot afford Microsoft license fees.