I'm in a similar situation. I think if you read a lot of HN and are reasonably successful, your expectations for life can get detrimentally high. And what happiness and meaning you experience largely depends on what you expect. You're already quite successful yet you're probably very unsatisfied. We read so much about startups and these amazing projects other people are doing, but it's hard to understand what you should actually expect from yourself and your life — are these reasonable things to aim for, or even to just dream about? We're only seeing the survivors and successes, not the (how many?) others.
You could try planning for a longer break or vacation to see how you feel with more freedom, do you still want to do something "more meaningful" or do you actually miss work?
Even more than HN, what meaning you find tends to depend on the people around you. Imagine how some people in objectively much worse positions than you can despite that find much more meaning in their lives than you; usually because of the bonds they create with other people. (If you ever watched Star Trek or Futurama, remember how it wasn't the stuff the characters did that made it meaningful, but rather the characters themselves and their relationships..) Your social influences can be hard to change, but that's how it is. Meaning comes from being a part of something. Stuff you do on your own requires so much more effort to reach that same level of meaning.