Regarding the review process ... one thing that I find challenging and don't know a good solution to is documentation. I've received many PRs where the change itself is fine, but the PR is dragging out because the documentation is lacking, and getting the PR author to improve it sometimes takes a lot of review rounds.
What would you do to avoid this?
Sometimes the same situation comes up with tests, but it is not as common in my experience.
Get people to write the docs first. Not many people like writing docs after the fact, and much of the value of working documentation is lost if you do it after the implementation.
Assuming we’re not taking about user guide kind of docs, then a major benefit of writing docs first is to clarify your thinking. Being able to explain your intent in the written word is valuable because you will often uncover gaps in your thinking. This applies to a specification, or to acknowledging problem reports and updating with theories on what the cause of said problem is and an approach to confirming or fixing it. You can even reference that problem report in commits and merge requests. It pretty beneficial all around.
And docs don’t have to me masterpiece works of art. Just getting people to clarify intent is a huge win. Peer reviewers don’t have time to do a super deep dive into code. If they know what you intended code to do, that’s something many reviewers can check pretty quickly without having to know much context.
It’s selfish and naive to disregard basic documentation of intent.
One option would be to take an initial stab at the documentation yourself - that makes it clear to the submitter where things are unclear, because you made mistakes or omitted things, and they can just correct that, which is a lot more feasible to do than figuring out what's important while your head is in the code.
What would you do to avoid this?
Sometimes the same situation comes up with tests, but it is not as common in my experience.