The seniority system is an odd one although I suspect until all airlines end it, it will persist
a few years ago while living in New Zealand I got chatting to an ex Air Force pilot with 25000+ flight hours on a variety of aircraft under his belt. He had recently joined air nz as a second officer (=first officer at BA). On his first flight after being checked to line he is shocked to find the man sitting in the captain’s chair is someone who washed out of the same military flight training cohort. In the FO (= SFO at BA) seat there is a 25 year old ex cadet with maybe 5000 flight hours
now in a merit based system it’s entirely likely that the seating positions would be quite different, and I suspect the public would be surprised to hear that it’s how it is
however. This bloke was all in favour of it. He felt that changing to a merit based system was just an avenue for shenanigans