It's funny, it seems that people feel more of a need to respond negatively than positive. Because if you don't like something than you feel more need to take action, if you like it you just enjoy the experience.
That positivity is a given and so people need to take action and speak out for negativity to have a presence. I think the issue is that some people equate silence with positivity.
People are more likely to comment on something they don't like, than to share a positive comment on something they like.
But I think that negativity has far more of a presence in the world than the positive. Daily life presents a lot more negative elements readily than positive. It is far easier and more likely to unintentionally encounter a problem or a bad situation than for something good to just happen to you. Good things and positivity require work and intent.
Generally speaking it's true that something that is wrong needs more attention and change than something that works. But the world bends towards negativity and it can be worth speaking up for something you like, not necessarily to change it, but to give positivity a presence at all.