My abiding memory of a seniority airline, is the CC, made up of the most senior pilot 'reps', feathering their own nests very nicely thank you, always at the expense of the junior pilots.
The disparity just got wider and wider, year after year. It was divide and conquer at its most effective. If there had been no seniority, their interests would instead have been aligned with all the other pilots.
Yes, we did try to get a junior bod in, but it wasnt easy, not least because they kept leaving, due to the terrible terms for junior pilots!