Removing the filibuster is a "nuclear option" - once it's gone, when the Senate inevitably swings the other way, the new majority will make use of it's absence

Removing the filibuster is a "nuclear option" - once it's gone, when the Senate inevitably swings the other way, the new majority will make use of it's absence to ram through whatever they want. There are arguments that this would actually be preferable and moderating, but that's a whole other debate. The 60 member supermajority was also fragile. And only lasted 72 days. There was a time limit on passing anything major. None of which is to say your wrong, only that there was a bit more nuance than "Dems had majority and flubbed".