As much as I’d like to say that a sense of proportion is a) developed to various degrees in different people and b) leads to a fairly consistent sense of what ‘works’ and what doesn’t, I think this is about as far from the truth as you can get.
This is an oft-repeated theme from photographers and, perhaps, other artists and wanna-bees.
The idea is that different people like different things, you can't please everyone all the time, so just do what suits you.
The last phrase is right, but the start of the sentiment is just a giant bloody excuse to give up.
What you decide you want to achieve is up to you. I do not presume to dictate. However, know that it is possible to make art that is universally appealing, it is possible to make art that is broadly appealing. It is possible to make art that is broadly appealing, as well as meaningful and powerful. It's not easy, but god damn it, it's possible. Falling back on some "well it's all just subjective innit" or "hey, tastes vary" or "most people just aren't educated enough" is just a damn excuse, and if you catch yourself using it, knock it off.
By all means, make photographs that are not broadly appealing. It's a lot easier, for one thing, and perhaps it lets you get to something meaningful without killing yourself, or perhaps you just don't care that much about broad reach. But don't tell yourself that it's impossible to do anything else, it's not. It's merely difficult. Perhaps it's beyond your capabilities.
But by golly, if you want broad appeal, go try for it. Reach for the stars, you wimp! Stop making excuses!