I’ve fully come around on socialists running as Democrats. The DSA is a political party in the traditional sense of the term, the Democratic Party is not.
The Democratic Party is not a true political party, with an ideology and dues paying members who it has the ability to exclude. There’s no requirement to join, and no way to be kicked out. All you have to do to be a Democrat is tick the D box when you run for office. The Democratic Party is an apparatus of the US political system, in the same way that the House of Representatives is.
My biggest issue with the DSA running as Democrats is that they should also be running as Republicans in districts where that makes more sense. In fact, the Republican party is even less of an actual political party than the Democrats, and has basically no system internally to exclude people they’d like to exclude. There are no super delegates in the RNC.