When I first started shooting I was underexposing all the time.
Then after Derrel, et all showed me the way I began to proper expose items.
Then I started learning more about the colors and how just a plain image is kinda drab for people. I initially learned by using the "AUTO" setting in lightroom. Then learned to do all the changes manually, then learned a little about curves, etc.
I actually pull down my blacks in many shots because I like it that way. But I understand what is going on in those photos for the most part.
but it's all about learning and experimenting. Have you played around with each and every slider in lightroom to see what it looks like before/after ?
Start learning the tools that you have better and that requires you to read and experiment with it.
I still will move a slider all the way to one side then the other just to see, then move it slightly from the middle to get an adjustment that I like.