Mitch McConnell weaponized the filibuster. Now he just has to declare one to require 60 votes for passage of any bill rather than a majority.
It used to be that a filibuster actually required speaking on the floor of the Senate, which is why so many Senators would read things aloud such as Green Eggs and Ham.
At some prior point in its history, the rules were changed so that Senators could conduct other business while the filibuster was active.
The filibuster has gone from being a delaying tactic to an effective veto.
Not only did McConnell weaponize the filibuster, but he also changed SCOTUS nomination confirmations to require only 51 votes. And he invented the Scheduling Veto.
That veto power used the Right of First Recognition when a bill was introduced. That right gives the first person recognized by the President of the Senate (usually the VP) to offer amendments, substitutes, and motions to reconsider before any other senator.
And, more importantly, to schedule a debate. By precedence since 1937, that first person is the majority leader, and it's not in The Constitution nor in the Senate rules.
McConnell's solution was to never schedule debate, no matter how popular a bill is. So the Senate is where House bills go to die, and it's more effective than a presidential veto since voting on a bill never takes place.
The Scheduling Veto was also used to deny Merrick Garland a confirmation hearing for a Supreme Court seat, enabling him to pack the Supreme Court more effectively with conservative justices.
