As much as manchin likes to say, democrats do not benefit from the filibuster. Tons of Republican issues are single issue nonsense that the majority of the country would detest if passed, so republicans rely on the filibuster to just not do anything. Forcing republicans to actually pass laws would be good for democrats politically.

The filibuster continues to exist because it gives people like manchin compete power, so the most moderate of each party will always try to keep it alive.