The filibuster is really a cloture vote. Cloture is supposed to mean “Let’s stop talking about this and get to a vote already”. A supermajority is needed for it, because the idea was that a simple majority might be insufficient to cut off debate before a vote, because the other folks might still have valid things to say.

Now, if the folks who vote against cloture were really interested in still talking about it, maybe it would make sense. But the way the fillibuster is used these days, when they vote against cloture, it’s not because they want to keep talking about it, it’s because they want to talk about something else instead. Thst shouldn’t be the point. They should continue to talk about the matter at hand until they drive it to a conclusion.

If I were King of the Senate, anyone who votes against a cloture bill should be recognized afterwards to say what they needed to say about the bill, and then they should be prevented from voting against the next cloture vote. After all, they voted “no” on cloture because they had something further to say, and then they said it, why should they gum it up further?