I agree with the sentiment that it's very easy to underestimate the harm done by the loss of a major site or scene group, but I'm not sure I really agree with much else you've written here. In particular:

And it’s due in part how most of the pirates just take and take, but never give back. On r/piracy and sometimes on here, people are making posts wondering where they can get free stuff and how they can get free stuff. They don’t care about the technicalities, they don’t care about the cause of piracy, they don’t care at all. It’s always “give me free shit, thanks, bye”.

The people making those posts have minimal exposure to piracy. This is getting your feet wet. For me, contributing my share is saying that I think these users deserve access. Yeah, they wouldn't have a place on a private tracker, that's not a problem because they're not on a private tracker, and if they join one they won't stay for long if they neglect seeding.

I'm sure a lot of these people will continue their lives without seeding or contributing. I won't say I endorse that, but I'm cool with it, and even if I wasn't I still don't think an argument can made that the harms of any hypothetical injustice here outweigh the benefits from a single dedicated pirate that began their journey this way.

I care about uploader counts, about seeder counts, about the wellbeing of the people who maintain the infrastructure. I'm invested. I don't care about download counts. Looking at an unseeded download as a loss in seeder count makes exactly the same amount of sense to me as looking at a download as a lost sale. I think it's morally right to support pirates who will not end up contributing, and beyond that I think treating them with kindness a net plus for the cause, because less than 100% of them will just say “give me free shit, thanks, bye”.