Very true. Most Americans don't know actually what socialism is, it's just a synonym for "bad." I don't think anyone that describes themselves as one is going to do well with most US electorates, even though the tenets of socialism line up pretty well with their actual beliefs.
The DNC is corrupt and sucks, but they're right to fear this association. If they embraced the socialist messaging today at the party level, they'd likely lose every election outside of the major metro areas and become even more irrelevant than they already are.
No argument there, but messaging is important to be effective. Most US voters are going to reflexively balk at the word "socialist" and will stop listening to anything else being said. It's unfortunate, but it's reality.
I think they'd actually agree with the tenets of socialism if they could get past the reflex though. For example, if "owning the means of production" were packaged as, "a fair share" they'd be more likely to listen. Silly, but you have to meet people where they are to be effective.
Mamdani talking about issues everyone but the rich would agree with is great, and I'm happy to see the upswell of support for it. I still think he'd lose in most other places in the US though, the word "socialist" just carries too much of a stigma outside the major metro areas.