If a function has 300 lines without a lot of supporting documentation then I doubt that it is “clear, readable and concise” anyway.

Code - not function. Files often have multiple functions in them. If you can't read and understand code - I don't want you on my team.

I have never found it hard at all to skip past comments that are not relevant because my code editor helpfully colors them differently from the rest of the code, making it easy. Does your editor not do the same?

If it's something people will simply skip over then it's not useful. Don't pollute code with tons of unnecessary comments that you think will be useful for some "perceived future". They just add to your maintenance work.

Write your code to be understandable and document the architecture/design separately.

It depends on what you are doing. If you are implementing relatively simple logic like a REST API handler, then it is probably overkill. If you are implementing a relatively advanced algorithm, then having a running narrative of what is going can be extremely helpful.

Agree - most code is pretty straight forward. Save the comments for where it's needed.