I probably wouldn't call it squatting, but it's something economically similar.
> Should its registrant morally pay more than the default annual registration cost?
Yes.
> If so: How does consistently using a domain (any domain) for literally 30 years (as of a week ago) for a personal website and an email address constitute "squatting?"
If someone's using a highly-in-demand domain for a small website visited only by friends and one email address, then I see that as wasteful and icky. It's like having a /8 IP block because you registered in the early days of the internet, and using it for your home network of 5 computers. Or having a giant mansion in the middle of town where you live in a couple of rooms and leave the rest to rot. Or owning a bunch of historic paintings/cars/etc. that sit permanently in storage and are never used or seen. More "hoarding" than "squatting" I guess, but equally gross.
I think the whiners who carp about its current use are just crypto-jealous.
If so: How does consistently using a domain (any domain) for literally 30 years (as of a week ago) for a personal website and an email address constitute "squatting?"
Please note that there is a significant time cost (both senses) switching one's email address. Speaking personally, I have found some organizations are effectively incapable of updating an email address in their systems, at least not on the first N attempts over the course of M years.