I agree with this. But I don't think code reviews are suited for this step 0 as you say. Just the way a pull request is formatted, it's very hard for the review

I agree with this. But I don't think code reviews are suited for this step 0 as you say. Just the way a pull request is formatted, it's very hard for the reviewer to deduce from the changeset what the high-level design of the code is. That's why we discuss these high-level design and architectural decisions before-hand so that they are known to the reviewer at the time of the review. We're a small team so it works well. But I'm not sure how this scales up as the team gets bigger. I would like to know how bigger teams approach this problem!