Once a contact unsubscribes, you don’t have (express or implied) permission to email them again… unless they opt back in themselves or initiate a business transaction with you.
While all of CASL may not be easy to understand, this is pretty straightforward.
The example shown here is a no-no. Depending on the audience, the reaction may be less severe, but I can’t imagine sending an email to everyone who has unsubscribed from my own newsletter over the years inviting them to come back. While you might not object, and some might resubscribe, I’d be asking to be flagged as spam – and rightfully so.
While it’s partly about respecting my fellow business owners, it’s also about protecting my own reputation. Like any other parts of your business, when you get a bright email marketing idea, think it through (and even research) before jumping on the bus.