Most instances may have an emphasis on an interest or affiliation but that doesn't mean most people are on such instances or pay it much mind. Most instances are quite small. The largest instances tend to be generic.

And people do mildly judge others based on email providers.

Only if you count generic providers like Gmail or Yahoo.

There are millions using @faculty.university.ac.uk style addresses, or employer addresses, club addresses, etc

If I choose to I could be using my local car club email address.

It's all evident in the domain name.