Frankly, the main similarity with CookieMonster are the icons I use. But the features are sufficient for my use. Cookie mess gets reduced, privacy increased.
Because Firefox is switching to Webextensions, it's impossible to create an addon exactly like CookieMonster, which works with Firefox 57 and later.
For instance Webextensions do not have access to internal Firefox permissions, which you can change through the icons on the left side of the URL bar. CookieMonster was able to access these settings, because it is a legacy addon.
It's currently also not possible to block all cookies through Webextensions. It's only possible to delete them right after they have been set.
If you think this addon lacks some features, you may want to try the addon "Cookie AutoDelete", which has a lot more features than this addon and will also work with future versions of Firefox.