Yes, the amount of tracking cookies is declining.

https://www.techradar.com/news/gdpr-sees-cookies-crumble-on-...

The shutting down of companies is a desired effect, because those are the companies that won't get consent. Data resellers for example that dont provide any advantage tto the user.

We haven't even seen the actual effects yet because google Facebook et al are probably in violation and are waiting to be sued to fight it out in courts