Good. You shouldn't trust my code until it's been reviewed. I don't even trust my own code until its been reviewed! I've gotten much better with time specifically because of the things I've learned from reviews, but having another pair of eyes on my code still frequently uncovers things I overlooked while in the weeds.
> Pull requests don't prevent bugs.
This is just wrong. It doesn't prevent all bugs, but nothing does. Reviews, testing, static analysis, requirements, proofs - they're all designed to improve confidence in software. They all work to varying degrees, but none of them are perfect.
> Pull requests slow down.
Good. This is a feature. If a change is big enough that it takes significant time for another qualified engineer to review, there's a high chance that an issue will be uncovered. At the very least, it ensures another engineer is familiar with the changes.
If reviews drag on because engineers don't treat them as high priority, then that's a culture problem - not a problem with reviews.