Seniority doesn’t mean you will be captain when time comes. Seniority assures that you will have the opportunity to prove you can be Captain when your time comes. You still need pass the check ride as any other pilot.
If you scrap it one thing you will have is hundred of pilots flying aircraft not in flyable conditions just to gain a promotion. Or to maintain it because you are scare that the company will hire new Taliban pilots because they are cheaper or they fly in any conditions.