You already do a great job. This process is inherently slow so no big worries there.

When I get extra slowed down, it's usually because

1. something is insufficient in UI/UX
2. I catch some obvious areas for improvement in terms of simplifications/idioms/code reuse/performance

These are on the subjective side for one and for another they're sometimes non-obvious depending on familiarity with the code and deps.

Even when the code is perfect, testing it, reading line by line, and then context switching from pr to pr is slow.