The strangest thing about .NET I think was the Windows Communication Framework which was ahead of its time in many ways but was hobbled by numerous choices that left it out of the mainstream.
A real long time ago (I think 2006) I was working on a web site product line that sold alcohol online. This is not fundamentally problematic (the delivery driver cards the recipient of the package) but you have to attend to details such as tax rates in various jurisdictions so we were shopping for APIs that would give us that information.
One vendor had an API that was pretty good but was based on SOAP and after two days of work I think I had solved the problem of making authenticated requests from PHP but there was still something broken, at that point we switched to a competitor that was using simpler technology and it working in less than 30 minutes.
I'd contrast that to the use of Jackson in Java backends where Jackson automatically generates a mapping between JSON and Java objects that "just works" most of the time and often you end up spending very little time thinking about serialization or being compatible with any popular clients. I'm sure ASP.NET has caught up, but I still think ASP.NET MVC would be overkill for the average backend for a React-like app. I have to admit that Sinatra-style JAXB in Java is so easy for that purpose.