People can always unsubscribe from your mailing lists
At work, every so often I get added to a mailing list where the people running the list are firmly convinced that it's so important that some or all of the recipients shouldn't be allowed to unsubscribe. There is no gentle way to put it: these people are operating under a tragic and dangerous misconception. The reality is people can always unsubscribe from your mailing lists. The only question is where they do it and if you find out about it.
Specifically, if you don't allow people to unsubscribe at the mailing list level, what inevitably happens is that people silently 'unsubscribe' in their mail client. Any modern mail reading environment offers several different ways of doing this, some of which you will like more than others. Unfortunately the way you will like most (or dislike least) is the one that users are the least likely to use.
The obvious and theoretically best way is to create a filtering rule that junks your mailing list messages (and if you're lucky, is precise enough that it only junks those as opposed to, say, all email that you ever try to send to them). The problem with this is that writing rules is kind of a pain in the ass so in practice the users are likely to use the easier approach, namely clicking whatever 'mark as spam' button their mail client has (it almost certainly has one). After they do this a few times, any competent modern mail client will silently start disappearing your new messages as spam. If you are lucky, this marking only affects mail to that particular user. If you're unlucky, what they're doing is helping to persuade a shared mail provider that your messages should be marked as spam for everyone.
In some modern environments the users don't even have to go this far. If they repeatedly delete your mailing list messages unread or barely read, their mail client is smart enough to learn from this and to start automatically categorizing your email as low-importance. Again, if you're lucky the system did this characterization narrowly enough to just take out the mailing list; if you're unlucky, it will take out more. The good news is that this will probably not reach out to affect other users, although you never know.
So on the whole you're much better off letting people unsubscribe even from mailing lists that you think are really important. At least that way you get to know if your audience agrees with you and you can rethink your efforts if they don't.
(In fact unsubscribes are a really good signal that your efforts are not working. You might say 'but if people unsubscribe we can't get them back with better content'; in practice this is almost certainly a delusion. Once someone has decided that your messages are not worth their time it doesn't really matter how they implement the decision because they're extremely unlikely to pay your future messages enough attention to reconsider it, even if they are just deleting them without any further consequences.)