This is just a matter of priorities - I use LLMs to write code every day and I have never put a single line of code up for review that I didn’t read and understand.

I use to do this and then do test manually to validate everything works as expected in my small open source project. But then over the time I saw that some bugs crept in which I was unable track since I was doing manual testing. So I wrote some e2e tests with playwright and I think that gives a bit relief (at least).

While I'm sure you're speaking for many, this is definitely not true across the board.

Not to mention that manually writing code is itself a process of understanding. It cannot be replicated by reading code, no matter how carefully.