Would you be able to maintain your sense that a painting was good even if ten or more people vehemently disagreed with you?
Do you have the internal strength to follow your own hunches?
If you don't, I can make some guesses as to why.
1. You have been wrong before. It is not that you lack passion and conviction it is that you respect the fact that emotion can cloud vision. I cannot count how many times I have been caught up in some aspect of a painting without being able to see that the whole painting didn't work. For years I had to get help to decide if something was good enough to mat!
2. There are too many art forms to be good at them all. If the time is not taken to master the basics in any art form then there is no solid foundation upon which to build true mastery.
3. Intimidation. You have been bullied by someone with strong opinions, made fun of for a perspective that was different from others, or been shunned by someone who was jealous...etc.
Nevertheless, if you think something is good have the courage to say so even though you will run the risk of being intimidated, uninformed or wrong.
The consequence of a life lived in suppression is a far greater loss.