The filibuster rule is a good one. But it is just a rule, and is nowhere mentioned in the Constitution. So a simple majority in the Senate can legally eliminate it.
That, of course, would lead us one step closer to disaster. But Democrats don’t care about that. They live in the moment, and tomorrow be damned.
Yes, the filibuster is essentially a ‘gentleman’s agreement.’ It does have the weight of tradition but that’s all.