It needs to start with responsible sellers. My local fish shop refuses a lot of sales because just talking to the customers they don't know what they are doing. 'had the tank running for two days' kind of thing. owning any pet is a privilege, not a right. Those who can't prove they have the knowledge and means to look after them need to be refused.
Sadly there are lots of shops that'll sell to anyone no questions asked.
Judging is easy, and I do it all the time. But if you run a small shop with one of the corporate giant Pet chains charging in, you are in a bind. Turn away too many customers, even for the right reasons, and you're dead. I've watched this hobby go from a situation where dozens of small shops run on a "make a decent living" basis by often knowledgeable owners have been crushed by well financed mega-chains.
Behaving like the chains isn't the way to go, but too many principles leave you applying for a job at Petwhatever.
Now, we answer by saying a well informed shop will survive because it offers knowledge. This would be fine if we saw a trend toward valuing knowledge, but what reality says is there's a trend to cheap.
I recently moved from a city of 3 million. Because of language issues, the large English speaking chains didn't want to translate their stuff, so they stuck to the English provinces around. The better shops are still in trouble though, as the conservatism of our hobby gives them no incentive to be different. If they offer something cool, it doesn't sell. You can argue I'm a little too into this hobby, but I've always been curious about fish. I find that curiosity is out of fashion right now. People don't have time to be curious?
A couple of new stores have done well there. One sells only mbuna Cichlids, and has a strong following, but the one with a focus on aquascapes went bankrupt. A new one doing well has a neat angle - it only sells wild caught fish from sustainable local fisheries. The fish are pretty healthy compared to farmed stock, but cost more.
So I'll throw your valid point about stores back your way. Those who have bothered to learn need to support local stores. Online buying is only for things you can't get locally. You go cheap, you get the attitude toward living things that goes with it - disposable life.
If you live 300 km from a decent store, yeah, you're stuck.