Well, that's kinda how it has to be, right? If art museums displayed the artwork anyone can paint, they wouldn't be interesting to most people. Most museums are about displaying the stuff you otherwise wouldn't be able to find, buy, or make. It's still fun to learn to paint, even if you're no Rembrandt.
To be fair, there are some museums that go for depth instead of scarcity and I personally find them more interesting. The Computer History Museum does this pretty well. They have some truly unique items, but also plenty of stuff you can buy on eBay, just presented and explained well.
It's very common for art museums in Japan to have a room dedicated to paintings from local residents. As one would expect, the quality ranges from "why would you show this to anyone" to "can't believe how amazing this is". I always enjoy going through them.
The Loudville lead mine in Easthampton MA, which used to be open for public collecting, recently closed due to irresponsible collecting and severe erosion. They closed off the entire recreational trail system, which has far reaching affects far beyond the rockhounding community.
I'd collected once at Loudville shortly before it closed and found a couple scraps of Pyromorphite, some tiny Wulfenite you need a microscope to see, and some Malachite. I am sad that I can't go back, now.
You can read more about it here: https://newenglandforestry.org/newsroom/recreation-on-the-ro...
I don't expect, or really even want to find museum-quality specimens, I just want the ability to explore the minerology of my home region on a physical and personal level.
Most of the ones I've found were incidentally discovered while hiking around off-trail in the boonies. I do always bring my Estwing with me just in case though.
Just this past weekend I pulled a plate full of rare tellurides out of Otto Mountain for a Caltech PhD. You have to be very observant to find a good spot to acquire minerals out of the ground, but excellent large specimens are still out there to be pulled.