I know that feeling all too well. If I one day get good enough to the point of making my own, I am sure I would very very rarely them 5 stars unless I genuinely believed the were on par with others I would rate the same. I've always been my own worst critic, but the one good thing about that is that I usually push myself to do even better.
However, I am just like you, much much nicer and less strict when it comes to other people.
To the OP though, that sucks. Like I completely understand that if you make something and you genuinely believe it is good and worth 5 stars, then you should be allowed to give it that. Honestly, it just hurts the whole system to not rate a good recipe highly, most the time those are the ones that will be made anyway, so we should want good stuff to reach the top, helps everyone... like why be a douche about it
Oops just realised how old this thread is and how old that comment is... sorry.