It's OK... It removes some stuff, but definitely not all—even stuff it can select, which is mysterious. For example, the annoying fold-out, non-closable sidebar here:

https://kwiklearning.com/memory-series/fix-forgetfulness-fast.php#

It can select (highlight) the sidebar, so it knows what code's generating it—so it should be able to block that code, right? You'd think so, anyway. But no. Go figure.

[Edit] I'm afraid I've had to lower my rating to 2 stars now. This extension used to be great, but it really seems to have fallen behind.