The problem is that what you're buying is a license. Of course it has to be a license, because unlike a physical good, anything delivered digitally could be replicated infinitely, and of course you wouldn't be allowed to do something like open your own storefront to resell copies of it. Nor would you legally be allowed to play it on the radio, as background music in a store, etc.
"Buy" isn't really that different here than if you bought a ticket to a concert; of course you wouldn't be able to attend next year with the same ticket, but you still bought something. The problem is that with digital licenses, they can be INCREDIBLY varied, and sellers don't make even a small attempt to clarify what the terms are.
You use the word ownership, but at least from a legal standpoint, that doesn't really mean anything intuitive, unless it means you hold all rights to the IP (which, again, you don't). It would be nice if there was some widespread legal definition and norms about "ownership of a digital copy", but no such concept exists, and frankly the rights holders are not incentivized to try to create something like this.
Part of the problem is that court cases don't materialize from nothing. A judge can only rule on a case before them. So you would need someone to bring out a specific complaint against a specific party. So there needs to be a lot of money on the line for someone who actually feels they can win. A class action against all online media storefronts just isn't that.
Also, it's a difficult case because the terms of the legal license that each customer are being asked to read and agree to ARE being upheld properly -- so you either have to make the case that asking a customer to agree to terms digitally that they've pretty please read isn't binding (which kills all digital commerce, because it all becomes a liability nightmare!), or, that the website etc is materially misleading / misrepresenting the agreements; we've talked about consumers maybe being prone to misunderstanding "buy" here, but I really don't believe it's a legal slam dunk.
If anything, the faster path to improve this the way you're looking for would be legislation.