Seniority is a terrible curse for pilots, and I just cannot understand why any support it. It stifles the job market, reduces pay, and leaves pilots stuck with a particular employer. Without seniority 'strong unions' would not be required.
Proposing Ryanair and the likes as a reason to maintain it is a falsehood. They tend to get stuck at RYR because of other companies seniority systems, so are open to abuse by MOL.
Even the senior pilots who, according to some, are the beneficiaries of this nonsense don't actually benefit.