I've heard all the arguments. I get it. I just think you're wrong.
But let's assume you've heard all that and are just as sure that I'm wrong. That's fine.
I was once a smashing good mysql DBA. Because I needed to be. Now I am not. Careers aren't linear.
Individuals don't build or support products. Teams do.
What kind of people are attracted to a job advertised in such an aggressively exclusionary fashion? Only a small fraction of the overall pool of exceptional engineers, I'd wager.
Having an excess of self confidence isn't necessarily correlated with possessing the engineering skills one needs to do the job.
But as you grow, I wonder if you can continue to source as many "super senior" engineers
If so, i think hiring juniors would be an excellent and meaningful lever for change.