I see both sides of the argument. I’ve worked in a non seniority based airline filled with nepotism where bloggs was a good egg from the squadron mess so
lets make him a skipper, yet had no place inside an aircraft let alone the flight deck. Then there’s Smith who was a rumoured trouble maker so let’s never give him a shot at even applying for command.
And I’ve seen seniority based airlines where you sit in the right seat till your number is up. You’re locked in to that company if you’re senior enough.
both systems have pro’s and cons.