We should probably realize that without a seniority system our industry could use the standard tool against organized labour, i.e. firing anyone who even thinks "union" before they manage to do anything.
Seniority is a problem in times of poor economy because it's lost when your airline goes under. This should keep pilots interested in the financial side of the business but sometimes that doesn't seem to work. Current events in the US show that pilots are quite willing to give up a lot to keep their company and their seniority alive.
I doubt that our profession would be where it's now without seniority, and I see that as a positive remark. Without seniority safety would be dominated by beancounters and we'd have premiums and promotions based on "willingness to do overtime", "no diversions" or "no extra fuel taken".