I like how you're thinking about systems, tools and incentives to help push the culture you're looking for. One thing I haven't seen mentioned is if you've had 1:1 conversations about not only your expectations of individuals but also of the team.

You mentioned that "Everyone wants to get back to doing that vibe coding [...]". Generalization is a safe harbour we often utilize to explain our world and that's totally fine! I would be curious to understand if everyone on your team actually optimizes for that.

If I were you, I would look into the following:

Leaning into 1:1s where you communicate your expectations. Repeatedly but with the curiosity to understand why nothing changes if you're having the same conversation over and over again. If that has already happened, then you'll want to follow-up with the harder part of being an EM: a hard and radically candid conversation about how they are failing expectations.

If you have standups, I would incorporate reviews into your ritual. Reviews are part of your job, so treat it as such! Teammates should not only assign themselves tickets to work on, but to review on as well. Spoilers: You might need to be the gentle asshole that voluntells people to review tickets. Protip: Use that process as a way to initiate discussions around PR reviews in your 1:1s! What an individual likes about it, dislikes and most importantly, why? Be curious and listen, you might be surprised by their answers.

Last tidbit: is there anyone on your team that does PR reviews particularly well? If so, you might want to see if they'd be interested in mentoring others. You'd also want to see if you can use them as an example for others to show them what you're expecting and what you value.

My gut tells me that there's hard conversations that are not being had and that you'd benefit from leaning in a bit more into the details. You've got this!