I'm a mathematics student just starting my third year. Since entering grad school, I have become rather firmly convinced that academia is not the place for me. The intellectual work is great, but the life side sucks. I hate the administrative bloat, the grad student/post-doc slavery system, being constantly surrounded by people with no social skills, the whole toxic self-sacrifice culture. I think I want to just go into industry, find myself some niche, or work my way up a corporate ladder. Probably in tech or finance since that's who needs mathematicians.
Problem: my research area is real pure, pretty much no direct applications at all. So, since deciding to go into industry, I've started to look at another field which I have taken a class on and is interesting to me, but I don't really know very much about yet. It's a relatively new discipline which has seen recent applications in data. There's a couple of people in my department who do related work so I might ask one of them to be my advisor. (I don't have one yet- the first two years here are very coursework heavy and this is the semester to choose.)
The trouble is, I feel like I'm starting back at square one. I fell in love with my original field during undergrad and have been going hard on it ever since. I was research-level before entering grad school, published a paper in top journal, had a bunch of ongoing side projects, and have read enough that I can easily hold conversations with professors about most topics. I know 100% I could bang out a thesis in the next three years if it was in this field. I even have an original topic based on a generalization of my earlier paper, and have made some progress on it on my own.
In my new field, I feel like a beginner. If my peers in the new field have the same level of expertise as I did in my original field, then I'm way behind. I might take longer to graduate, or have a crappy thesis. Or maybe I'll discover I just have no talent in it, that my brain is only built for original field. I don't know.
I am very confident in my original field, but from an applied perspective it is useless. Is it worth anything to get a PhD in a pure field if you know 100% you're going into industry? Would it be worthwhile for me to attempt to change to something more relevant in which I am a beginner?