Then how are they considered to be democratic at all? I thought that was a requirement for DSA...

Of you asked the vast majority of DSA members today, they would say that the "Democratic" part of the name refers to the internal processes of debate and mass democracy that the orh practices internally, rather than, say, a commitment to a reformist path to Socialism.

First of all, how is running a political candidate based on popularity strategically flawed? That's literally the definition of being politically strategic.

Popularity can be important, but the key criticism here is tailing an individual. AOC's relationship with DSA is complicated, and for many in the organization, that communicated relationship means that going all in on an AOC presidential bid would be putting the cart before the horse as it were.

If she were to win, there is neither the movement infrastructure, nor a significant or coherent enough Socialist bloc in Congress yet, for her to get much of anything done.

Further, given her previous votes for selling "Defensive weapons" to Israel, many on the DSA left believe, and I think rightfully, that when the institutional inertial of the military industrial complex inevitably drags the US into a conflict in some far flung corner of the world, that she won't have the backing, nor the personal fortitude to stand up to something like that. I think such a thing would tear the whole Socialist project in this country apart, frankly.

Secondly, AOC is perfectly capable of leading and educating the masses;

I think a failed AOC run could be instructive, in ways similar to Bernie's two runs. The Bernie campaigns failed, but they were successes insomuch as they brought back Socialism into the American political consciences, brought people into DSA in droves, and radicalized those new DSA members away from their former liberalism.

Perhaps a failed AOC presidential bid could do something similar at a larger scale. But I think that's the extent of such a thing's utility. I think those in the org who are diehards for an AOC presidency (namely Groundwork caucus) aren't thinking as far ahead as they ought to.

moreso than any delusional MLs lurking in the DSA without participating beyond complaining about every single candidate who actually runs...

Red Star, the ML caucus, has 3 seats on the org's National Political Committee, and occupies one of the national co-chair seats. Far from "Lurking" and "Complaining" in lieu of participating, they're a very active and influential wing of the organization.