From my hobbyist perspective. doing mostly street & portraiture with occasional event, of those I shoot, exceptional are ~1%, and worth a print.
Very good are ~5%, and they may or may not be printed.
Good ones are 10-20% - those are usually good enough for social networks.
This doesn't include any experiments with lights etc of course, since success rate for those cannot be measured - it may be a trash photo, but it may also give me a better understanding of how light works which is a success for me.
Also, since I have shaky hands, there tends to be slight motion blur that's not pleasing on ~30% of quick photos I take, which irritates the crap out of me, but I can't do much about it sadly :)
You can try with a piece of plexiglass or something similar, that can be bent. At certain angles you might get similar flares