This sounds very familiar to me too, I used to say I had many acquaintences and not so many friends because my interactions only went so far. I was very good at enabling people to talk about themselves (prompting with interested questions) but not very good at opening up myself so conversations would just dwindle.

What I found was if there was something I was passionate about I could talk a lot more in depth. So in my case this was sport/exercise and volunteering - it's no mistake my closest friends were made through those activities.

If you haven't already tried it then you might find it helpful to base conversations around your interests and activities, something you are passionate about.