I understand that not every product can be free and open source but honestly requiring 30 USD/y to even open a browser extension without any chance to test or expose the 5% of its features for free is ridicolous.

It's requires payment to unlock. No features work without paying for it, which should be made clear before users install it. And to add insult to injury, it's not a one-off payment, but a $30/year subscription instead.

Fully paid extension, no free features. Listing implies otherwise.

all 5* reviews are fake :D this extension is a scam

does nothing but direct to paid site

This extension is fully paid, require activation key. Not free at all. even no demo or free trial to test, time passer.