I thought about an idea related to this. What if there was some kind of a browser extension/app that detects and notifies you if you visit a site that uses dark pattern or have been known to employ stupid tactics like "send us an email to cancel paid subscription and we will get back to you". May be make it more specific use case when you are actually trying to sign-up or entering your credit card details, then notify you of their shady practices. The information will be submitted by users themselves. So if you come across a dark pattern site, you immediately click "Report this" and may be even fill in the criteria like "cannot cancel online" with some comments. It then gets centrally stored on the server and everytime another user visits that same site who has installed this browser extension, they get a minimally invasive notification of some sort ?

You have to work with white-lists, not black-list when dealing with such high numbers of shitty apps. In theory this should be done by the app store provider, just let in non-malicious software.

Make a blacklist app!

I'll definitely do it even if there is a little bit of interest. I'm thinking a small set of check boxes that you can click for an app ("spams contact list", "downloads your email" etc).

A subreddit-powered blacklist app so people can submit the what & why!

LinkedIn is one such app that should be blacklisted.