They sound like incompetent business proprietors. When did having a website become something exclusively for old people? Millennials are in their 30s and 40s.
It's more that having a website never became a thing for many businesses in the first place. 30 years ago they might have had a listing in the phone book. Nowadays that kind of business might have a facebook page, or more recently an instagram account. Creating a website (even with something like wix) requires a level of skill and effort above that.
I’ve seen a lot who are still paying for a site but rarely bother to update it. All the traffic’s on Facebook.
If you don't like it, that's your problem, not theirs. You're part of a small enough group they don't care about. I'm not sure how that's an age question in the first place, though. The "being run by millenials" throwaway by GP is just... well, at best, sloppy thinking.
There are GenZ businesses websiting, there are boomers insta-ing. You pick the tool for your niche.
All the information is already on google maps and IG/Facebook.
They have 2-3 billion people in their target audience.
And the point isn't if Wix is hard or not. It's that they answered the question "where do we need to advertise" for themselves, and just because you don't like it doesn't mean it's wrong.