Back in after 15 years

I played semi professionally, when my daughter was young. Cash games, at different casinos, in my home city. They were soft games, during the day, where old men played way too tight. I did alright, but during a down swing, I decided to give up.
I've played recreational, from time to time. The last few time I went to play in a cash game, I couldn't understand the playing style. I'd hadn't really kept up, but heard that game theory was now a huge part of the game. So, I've spent the last 3 months going over the theory. I don't know if I'm going to play well, but I'm excited to be back.