"communism doesn't work because communists are doomed to repeat the same exploitative power structures of the capitalist state">
I'd love it if you expanded on this cause i've been on this massively ML dominated space for years and still haven't been convinced that they're not (though i was always an anarchist so that might not matter that much). One of the main function of a state is reproducing it's power, that's why it can't wither away, especially in a world dominated by capitalist mode of production where communist states are forced to develop their productive forces.
"we dont know what an anarchist society will look like we gotta wait til we get there!"
We don't know what a communist society will look like either, mind you, we have blueprints at best. I posted an essay a few weeks ago about revolutionary spain and how anarchists there organized themselves and they definitely were getting there. You can check out Diego Abad de Santilan's writings to see a pretty concrete vision of how they wanted to make things work (though he's somewhat of a pariah cause he joined the revolutionary government, which is, yeah, not very anarchist).
Apart from that Anarchy Works by Peter Gelderloos (it's in the sidebar) is, while a pretty basic, but is another good example that shows why anarchism is anything but idealistic since it shows that the basics of anarchism together or separate were actually laid into praxis tons of times.
One thing to keep in mind tho which i see all the time is that anarchists have a different notion of what a successful revolution is than marxists, since their methods are different and i see this turning into a dick measuring contest still. For anarchists any revolution and any activity that creates stateless bubbles is a success, even if it's crushed in two years. That's why i specifically can't look at the USSR and say it's a success story, because while it existed, the state never withered.
Apart from that, what i think is also a huge and catastrophic misunderstanding is that most MLs still think On Authority is the greatest gotcha ever existed, but in my opinion doesn't do anything apart from conflating authority and force. Anarchists have proven thousands of time since it was written that they are very willing to use force against capitalists and fascists but biting the hand that beats you in itself is not an authoritarian act. What anarchists didn't do is setting up state structures where everyone's every step is monitored and you're encouraged to snitch on your friends and neighbours. Yes, i know we live in a system like that currently as well. That's why i say, from an anarchist standpoint there's no difference.
So yeah two critique's of Engels i've found interesting is this one and this one.