I consider Little Snitch to be simple-to-use... but you can easily cause problems by going overboard with blocking internet communications, with apps that require internet to even work. Regardless of what you do, it's something that you should always consider
There may be simple solutions, but sometimes, "one simple thing" may not necessarily be the result of something "easy". (Doing something easy to get a simple answer, is what I call a happy result.)
You do (I think) want a solution that is effective (does what it says "on the tin") This may take some thinking time, and maybe some effort, trying different solutions, until you get the result you want (that "one simply thing")
Just don't shoot yourself in the foot by blocking internet when that potentially keeps your app from working properly.