As much as I personally dislike Bernie/AOC/etc, I don't let those feelings overwhelm my commitment to ML.
History is long, the laws of history operate on timescales that we're not accustomed to thinking about. Social democrats have been around for as long as capital has been around, and as long as the laws of capitalism are in motion, social democrats will continue to exist. The laws of history operate regardless of what your feelings are towards them, so there's really no point in putting emotional stock into being frustrated with social democrats.
Yes, it is frustrating that their followers won't learn about the history of the second international, but it doesn't change the fact that a certain segment of the population will inevitably be drawn to reformism, i.e., the path of least resistance. The reemerging of social democracy in the US is the very beginning of a radicalization process that will take decades more to continue.