I dropped out of undergrad to work in CS..and in my early 30s looked around at all the startups and said 'this is all crap, I want to try to do something real'

so I did manage to get into a PhD program at a good school. happy I did, I took all the graduate courses and filled in all kinds of gaps. but at the end of the day I looked at all the grad students putting together half-assed little projects on their own to try to get published and said 'this is all crap, I want to do something real'

I agree with everyone here who has said 'figure out why first'. you can do research on your own - and there are very few places left that would pay you to do it even if you did have the PhD.

edit: also don't underestimate how awkward it is to be older than your peers with a decade+ of industry experience. you really are coming in from a very different path and its not always appreciated. I found trying to talk about people about code to be particularly frustrating.