The problem with /etc/hosts is that it is too easy to simply undo. I use https://selfcontrolapp.com, which lets you block a list of sites for a set period of time and does not have a way to circumvent that.

Well, since the app is open source, you surely could just read the code and figure out a method. However, doing that requires enough focused effort to source-dive and debug something. It is much much easier to prevent oneself from doing that than to keep oneself from editing a file.

If anyone is thinking of responding to this comment by speculating how to circumvent the tool, take that to another thread.