I'm in the industry right now, and while there's certainly room for innovation and improvement (our company was one of those originally), anyone considering it should know that this industry is a huge legal and regulatory quagmire, which makes diving into it difficult if you're not already familiar with it.
Despite knowing a lot about how it works after being in the industry for several years, I don't think I'd have the stomach to take a stab at a startup in this field myself. I've already had to deal with it over the years as an systems engineer and I'm pretty sick of it.
Also, if you're planning to do business with the big companies in this field, at least from the standpoint of my company, they really drag their feet with signing any business deals with you, and just about every company doesn't really want to pay you to do anything. We've had multiple companies back out of contracts (or act like they're going to sign once things are negotiated, then don't), even after we've done significant development (in one case building a whole system for them) and not pay us for our work, and then have the gall to ask us for parts of the code afterwards.
The only reason we did that work also, is because there are some crazy hard deadlines with open enrollment and the process drags so much that by the time everything is signed the software basically already has to be complete immediately upon signing if we wanted their business or else it would miss the open enrollment window (or pre-open enrollment, or whatever else hard deadline they had).
Also, the industry has been upended and thrown into chaos with Obamacare, and if the Republicans ever succeed in repealing/replacing it, then it will probably be thrown into chaos again. This creates an opportunity for startups that can move much quicker than these behemoth companies can move in reaction to these things, but it also means that you could be building a business on top of quicksand, and might have to make significant and expensive changes yourself in a few years if it changes underneath your feet as well.