> I guess my question would be, what's an example of this.
I don't know if this is exactly what your parent had in mind, but I found it relatively difficult to make a REST API. I had to work around a lot of things with model binding and routing to come up with my solution, and even after that, I still find it kind of hacky. In addition to that, IIS fights you at several points along the way, for example by adding spurious HTTP headers or doing things like automatically redirecting certain status codes.
With a framework likes rails, this is baked right in. With the PHP framework I used to use, the framework was so transparent and lightweight that it was trivial to bend it to my whim.
A lot of this was exacerbated by the fact that it was much harder than it should be to set up my project to use the source code for the framework that it should be. In thoery, you just grab the project from MS, add it to your solution and change some references, but in practice, if you're using any other libraries that were built against the DLL from Microsoft, you run into issues, because the MS DLL is signed, and the DLL you build from source is not.