Have you ever worked with the general public? At least half of adults would fail at that basic task.
The point of a business is to make money. You make more money by making the experience for your customers as easy as possible. If you don't, another company will.
If someone wants to unsubscribe, that's probably because they don't want to be your customer any more anyway. Unsubscribing for a now-irrelevant-to-them e-mail list may be a problem for these ex-customers, but it isn't yours any more.
The point of a business is to make money. You make more money by making the experience for your customers as easy as possible. If you don't, another company will.