The Constitution gave the veto solely to the President of the United States. And yes, it also says that each house of Congress can make its own rules.
The current form of the filibuster is in all essentials a usurpation of the President’s veto right by all 100 Senators. Any one of them can stop any action by the Senate for any reason, or no reason at all. And just as with the President’s legal veto power, it takes nearly a 2/3’ds majority to override any other Senator’s “Veto”.
Obviously, there are probably lots of Senators who are secretly not willing to cut off their own source of power. But…. could the courts be used to challenge the filibuster as an unconstitutional usurpation of power by the Senate?
Dream on, I guess