One of the things I find about Amazon is that it is pretty easy to cancel and resubscribe to things on it and their customer service is pretty generous on refunds. I guess I can see the enrolling complaint, but even there Amazon's design is far from as egregious as other platforms in terms of tricking people into subscriptions/making it hard to avoid subscribing.
Amazon is aware of how many folks accidentally subscribe to prime and never use the benefits. Someone did a huge project showing how many calls they get, money refunded, etc and the response was they didn't give a shit because they were raking in so much free money.
Don't know if it is still that way but for a while it was hard to set up an Amazon device without signing up for a auto renewing prime trial if you weren't vaguely tech savvy, and outside an iPad guess what is the most common first time tablet for the elderly?
I don't know if any of this is illegal, guess would be probably not but Amazon is very aware of what they're doing and it is very intentional.