Opportunism the way I like to approach it is be as left as you can possibly be in the political arena without totally abandoning your ability to get anything done in that space, and still remaining accountable to the socialist movement overall. I definitely have criticism for both AOC and DSA as a whole in it's ability to maintain this sort of stuff, but they are definitely trying. It's a lack of attachment to theoretical principals that is holding back the movement in a major way.

The most important thing is that outside this legislarive arena you are supporting major grass roots type efforts around mutual aid, left media, union building, and protest movements such that they become full vested parts of your left wing political machinery. The difference between the squad+Bernie and the most left wing legislative members like Barbara Lee is that they do make at least some effort in building out the above. Both the squad and DSA are far worse at doing this sort of stuff given their resources than Sawant/SAlt, PSL, ect, but they are doing it and it's why I still consider them to be left of succdem. DSA and squad democrats are much better at doing this sort of thing than a future third party like MPP or the green party does.

Also Sawant can be further left wing in the legislative arena than someone like AOC by virtue of the fact that she's one of nine in coalition with 6 other socdem legislators, rather than 1 of 435 in a split government. Someone like Sawant would be totally ineffective in a legislative body that large. The real test comes once we see a DSA type figure hold an executive office like mayor or governor, but until then, there's really not much more we can expect.

Most anger people have towards these folks is that they aren't constantly just shitting on democrats, and I don't think it's necessary that such rhetoric comes directly from them. They regularly are having their staffers leak stories to their media allies that shit on democrats.