That wholly depends on your definition of interesting.

I don't have a PhD.

I've written software that taught literacy to kids, helped people pay their bills online (back in 1999, when this was novel), written full ML systems (15 years ago, before the advent of open source ml packages), co-founded a YC company, and now I'm helping people rediscover the images of their lives (see my profile if you're interested!)

To be sure, I'd love to go back to school. There's so much I know I don't know, and would be wonderful to discover.

Just realize you can work on interesting stuff if you look for it, are willing to stretch your skills continuously, and change jobs every handful of years.