What are good/emerging fields to get into nowadays?

Particularly something that a 28 year old could take and have a career in without feeling like he's behind?

I'm currently working at a small tech company as a manager, and even though I'm a generalist (as I have a hand in almost all areas of the company), I realized that I want to be someone who is really good at one thing or at a certain area. A specialist, so to speak, as these are the sort of people I admire.

Doesn't strictly have to be tech. I'm just really looking for any course/specialization/field that I can learn, sink my teeth into, and potentially make a career out of.

One of the options I was thinking of is to learn how to be a web developer since I'm already in a tech firm. The problem with this though is that feeling of being "behind" since I'm starting to learn at 28 years old while people in my country have been coding since they were 18. I know that I can get over this feeling if I really put my mind into it since I have skills that other people don't have, but I wanted to see if there were other paths that I could take.

Any suggestions? Thank you!