In the end, they're just individual opinions, and that's the way you have to look at it. And the only opinion that truly counts is the client's. If you're just shooting for yourself, then YOU are the client, and if YOU like it, be happy with that, no matter what anyone else has to say about it.
You will NEVER make a photograph that EVERYONE will like, because tastes vary from person to person. With every photo you make, someone out there will or would absolutely LOVE it if they saw it, while others would suggest that you throw it away and make something good. The majority of opinions will be somewhere in between those two extremes.
There is value in the Rembrandt, the Picasso, the painting made by an elephant or gorilla, the child's first crayon drawing on the fridge or in the scrapbook - just not to everyone who sees them. The same is true for every photograph ever made, whether by an accomplished photographer with many years at it, or by the amateur photographer just starting out.
Welcome and receive all comments and criticism from all of them, but don't take them to heart. Thank them for taking the time out of their day to look at your work and give you their thoughts, whether you agree with them or not. Remember that they're just individual opinions and suggestions, no matter how they're worded, no matter if the person writing them acts snooty or snotty or knowledgeable or humble in their approach, no matter their background or education or age or ability; In the end, they're still just individual opinions about that one particular individual photo or series of photos, and even so-called "experts" will argue over the merits and details of various aspects of that which they are critiquing.
If you want to make photos that appeal to the masses more than to your own sense of what appeals to your personal tastes, then you have to learn and follow the "rules" of composition, posing, lighting, and so forth. Many will love the results, while others will describe them as boring, trite, banal, kitsch, etc.
If you want to make photos that appeal to your own sense of what appeals to your personal tastes, but those happen to be at odds with what generally appeals to the masses, it's still recommended that you learn the "rules" of composition, posing, lighting, and so forth, so that you understand what "rules" to break and when to break them in order to achieve your personal vision. The masses will probably not be impressed, but art critics may consider it avant garde, ground breaking, bold, innovative, and so forth.
The thing about these "rules" is that they're really guidelines toward what most humans find aesthetically appealing. They're not "rules" in the sense of the laws of physics; Things that cannot ever be broken. Those who are just learning these "rules" tend to see everything only from that one perspective however. So, in their minds and critiques, they think EVERYTHING should follow the rule of thirds, for example, and they haven't quite gotten to the point where they know yet when that rule not only can be broken, but probably should be broken. Keep that in mind, and use it when it seems fitting to your sensibilities, not every time someone says it in a critique.
Again, it's all just opinion, and you have to keep that in mind. You don't have to agree with all of it, or any of it. Take the gems that make sense to you and use them in future photographic endeavors as you please. Discard the suggestions that disagree with your own tastes and sensibilities just as easily. You don't have to tell the person giving the suggestions whether you agree or disagree if you don't want to. There's no sense in having an argument about it, after all, since it's just individual opinions anyway. You like it one way, they think it'd be better another - so be it. No skin off anyone's nose.
Yes, some have a LOT of experience, degrees in art and careers in photography, graphic design, and so on. They're "experts", they know all the "rules", and some are quite snooty and opinionated, as though it's NOT subjective to individual tastes at all, and they are RIGHT DAMMIT!!!
Yeah, right, Siskel, Ebert and Mr. Blackwell all rolled into one. Whatever you say...
There's no sense arguing with them or taking what they say to heart and carrying it around with you if you find it insulting. But that goes for anyone's critique, no matter how "accomplished" they say they are, no matter how big their egos, no matter how much others may seem to like or agree with them. Try to look past the snotty way they say what they're saying, look for any gems of information you can take with you, and walk away with those and the satisfaction that you're doing what you like, having fun with it, and learning more as you go, as are we all, no matter what stage we're at.
Those that think they know everything have simply stopped learning, and are generally bitter, crotchety, lonely, old turds, and that's why they come off the way they do. Just remember: That means they're already getting their reward for it: A pretty crappy day to day existence, whether they'd admit it or not.
Just toss that negativity from them aside like last week's wet newspapers, and carry on with your head high and a smile on your face like their opinions don't matter at all - because they don't - they're just opinions.
Have fun with it. Boldy submit your photos, take the gems, ignore the crap, and enjoy the learning process that will make you ever better.