> It feels very much like leading a team of junior engineers or even interns who are very fast but have no idea about why we're doing anything

Yes, yes!

And this is problem for me, because of the pace, my brain muscles are not developing enough compared to when I was doing those things myself.

before, I was changing my mind while implementing the code, because I see more things while typing, and digging deeper, but now, because juniors are doing things they don't offer me a refactoring or improvements while typing the code quickly, because they obey my command instead of having "aha" moment to suggest better ways