Yes, it should be cheap to throw out any individual PR and rewrite it from scratch. Your first draft of a problem is almost never the one you want to submit anyway. The actual writing of the code should never be the most complicated step in any individual PR. It should always be the time spent thinking about the problem and the solution space. Sometimes you can do a lot of that work before the ticket, if you're very familiar with the codebase and the problem space, but for most novel problems, you're going to need to have your hands on the problem itself to get your most productive understanding of them.

I'm not saying it's not important to discuss how you intend to approach the solution ahead of time, but I am saying a lot about any non-trivial problem you're solving can only be discovered by attempting to solve it. Put another way: the best code I write is always my second draft at any given ticket.

More micromanaging of your team's tickets and plans is not going to save you from team members who "show little interest in learning". The fact that your team is "YOLOing a bad PR" is the fundamental culture issue, and that's not one you can solve by adding more process.

I'm not sure what approach you're suggesting?

Asking a more junior developer or someone who "show little interest in learning" to discuss their approach with you before they've spent too much time on the problem, especially if you expect them to take the wrong approach seems like the right way to do things.

Throwing out a PR of someone who doesn't expect it would be quite unpleasant, especially coming from someone more senior.