As soon as the DSA is big enough to meaningfully affect the American political decision making processes, it, like any other democratic socialist party in history, will seek compromise with capital.

The DSA is not a party, and it's not even gonna get to the point where it can seriously threaten the system probably (although it wasn't EVERY democratic socialist party that compromised, see Allende or Chavez, more like succ parties, which granted, the DSA would be if it was a party). But that doesn't mean there is no point in organising with them and them growing in size. We must always take into account the current situation and what the vast majority of people can stomach. When people have reached a certain level of consciousness and class struggle reaches a level of sophistication, then we can talk about revolutionary parties threatening the system etc, and then we can discuss if x organisation is gonna fold and compromise etc. I believe that for the US the DSA is the best bet for something slightly more "centralised" (although the most important thing is workplace, college, community organising), and it's definitely useful for actual socialists to have a say in what is going on in there.

A revolutionary party is not something you set up and make. It is the result of a long process that comes about when class struggle has reached a very high level. You mentioned the Bolsheviks. Well, the Bolsheviks didn't come about until very late, they were all part of other parties and coalitions up to that point.