There is nothing in the world that detect/protect a system from everything.

Did you had PUP detection enabled ?

even though I had it installed my browsers are FULL of viruses
Those are not viruses, but malware. Blame it on yourself because you visited malicious sites/downloaded malicious things. The first line of defense is the user, not a tool.

Sending a email is not the way to cancel a subscription.
https://www.avast.com/faq.php?article=AVKB24

Posting your email address on a public webboard is a very good way to get a lot of spam.