Web focused dev isn't the only area with interesting problems but that's definitely what gets the most attention is frankly probably the most lucrative path for most people. I work in finance as well, and am kind of too specialized in it to switch now, but I do think I'd have been better off working at the FAANGs for my whole career.
If what excites you is web-focused startups, then yeah, you're probably not going to be happy in a lot of other places, but that is just one area of software development and I'd argue it doesn't have any exclusive license on interesting problems or top talent.