Blocksite previously got caught out for malicious activities and acting as spyware [1]. Unistalled it today and started using LeechBlock instead, which works way faster and has better features.
[1] https://www.tomsguide.com/uk/us/spyware-hits-11-million,news-27677.html
Blocksite moved to a freemium model too, so everytime you open the UI it's constantly trying to get you to upgrade, pretty annoying.

Buy PREMIUM to unlock a 5 star rating

Because the monetary program

Turned greedy. Bye

Uhm dudes? That some shady design decision to replace the quick-toggler (enable/disable) with the UPGRADE button to make people think they have to upgrade to enable blocking sites now. You have go into the settings to toggle it now. What a crap.

This extension collects your data.
If you are someone who cares about online privacy do not use this extension.
They were involved in a spyware campaign known as "Big Star Labs" (which is their company name) back in 2018 (search it). At that time their extensions were removed from both chrome and firefox but for some reason they were reinstated.
Remember if they did this before there is no reason they wouldn't do it now. Just look at the extension's permissions. They can collect a whole lot of data on you. I used to use this extension and really liked until now but this was a deal breaker for me.

Бесполезная игрушка.
Невозможно заблокировать рекламные домены.
Блокировать каждый рекламный банер вручную - кретинизм.
Когда-то это расширение работало, теперь оно - редкий отстой. Разработчик сосет у рекламщиков.
Не тратьте время.

https://adguard.com/en/blog/big-star-labs-spyware.html
Reported for abuse

totally useless

Sells user data

Wo bitte liegt da der Sinn, man kann Websites mit der Adresse sperren lassen oder durch einzelne Wörter. Soweit so gut, das man das ganze auch noch durch ein Passwort schützen kann ist genial, die Einfachheit würde auch schon 5 Sterne verdienen. Aber das ich einfach das oder den Addon problemlos im Firefox Menü deaktivieren kann. Ist wirklich ein Schildbürgerstreich, sorry, aber da fragt man sich wirklich wie weltfremd Programmierer sind. Auf die Idee einfach bei den Addons nachzusehen kommt wirklich jeder Teenager, gut gemeint, ich bin weder versiert noch ein Teenager, aber bei das Addon einfach deaktivieren,hatte ich auch einfach gemacht. Ein völlig sinnloses Addon

Bad performance on top of privacy concerns

aside from info i found after downloading about info selling (which i do not know the validity of). i put a site in my blocklist. i then realized i could change it to be a whitelist. so i remove the items in the blocklist, add some sites to the whitelist, and then switch tabs to find the whitelisted site is blocked for not being on the whitelist. ok, i'll just use the blocklist then. so i switch to blocklist and remove the site. and it then says the site is on my block list. neither of these things are true. i try to go to mozilla addon site to read more to resolve it. it is not whitelisted so i cannot connect, despite me being in blocklist mode. i know i am not that incompetent here so i am forced to assume either the addon is inherently bad or has some absurdly specific bug that renders it 100% useless. but either way i have no reason to use it

This company sells your private information.

Collects and stores user data.

I can't figure out how to use it.

Collects and sends browsing history

this sucks!!!

Simply not usable! Clicked "add to Firefox", but there is no 'dialogue box' to control this add-on! Hence. by design, it cannot work - and it doesn't. Complete waste of time.

i hate it