That is a logical fallacy. Yes, the Internet Archive lost a lawsuit because they violated copyright law. But that is completely unrelated to how licenses work. And itch.io is not in that situation here either- they have no legal reason why they can't keep distributing content that is being distributed in compliance with the licensing agreement, the licensing agreement grants users a perpetual license, and that license survives termination of the agreement with the publisher so even if the publisher says "Nope, not going to sell it anymore" the user who purchased should still, per the language of the agreement, have access to the content. And perpetual is, shockingly, perpetual, and that's the case of the license agreement here, so the "as long as it's granted" argument is irrelevant.
The only legal shenanigans going on here is that either the studio or the publisher (and with the publisher being Netflix, I know who I suspect more) said basically "Oh you can download it before October 1st, so you still 'have access' even though we're taking it away" but I think that's flimsy and I seriously doubt it would hold up in court- the license doesn't just say have access, it says "to use, reproduce, distribute, display and perform such content as permitted through the functionality of the Service." That seems to be a lot more expansive than the topic at hand.
It's also worth noting that copyright licenses are legally enforceable contracts, and unless those contracts have an explicit term (i.e. "You are granted this contract for the duration of [period of time]") I believe that in most jurisdictions those contracts would be indefinite (again, not a lawyer, but Google doesn't seem to contradict me). If you have a licensing agreement, you have to comply with the listed grounds for termination or you are violating the contract. Even a revocable license typically has specific criteria for its revocation (like materially breaching the contract terms) and can't be revoked without a listed reason unless the contract has "at any time/for any reason" clauses.
Now, having said all that, I'm going to say something that's probably more important. I'm not a lawyer, and I strongly suspect you aren't one either from the tone of your post, but importantly, I'm not associated with the platform in any way, shape, or form. I'm not saying this to win an internet argument, but if you aren't legal counsel to an organization, but are involved in something that may turn into a lawsuit, you shouldn't be speaking about it. I've been in a situation where I've been, by being a volunteer for an organization, tangentially involved to a lawsuit against an organization, and anything I said in any communication with anyone in the organization could be subpoenaed for that lawsuit, and while it never happened to me things other volunteers said was taken out of context and leveraged to make the organization look bad (which is bad legal practice since the context was pretty exculpatory but I suspect the point was to coerce the organization into settling).
Itch.io probably isn't liable for this (it would be either the developer or publisher breaching the agreement, if I understand it correctly) but they may be named as a party to a lawsuit given that their platform is involved in the circumstances and you have that shiny "moderator" name badge that could get you involved indirectly.
Best practices is to not talk about legal issues as a possible party unless you are absolutely certain that you are in the clear, because I can guarantee you someone will make your comments ammunition in a way that's very embarrassing for someone else and that will make it very uncomfortable for you. And based on the fact you're mentioning things like "Only open source licenses are perpetual and non-revocable by design" while talking about a perpetual license that survives termination of the Terms of Service you're probably not being cautious enough in your research or wording (and if you can find anything in the itch.io Terms of Service that states that licenses can be revoked, you're welcome to share a link, though I wouldn't encourage commenting any further per my point above.)
Anyway, TL;DR, don't talk about legal stuff when you have a shiny name badge because it will suck for you if it does go to court, even if you're not a lawyer, and also you need to do less association of unrelated things and some basic research before making an argument and you'll be a lot more convincing, or at least maybe know when to pick a battle.