Academics like Warren rarely run for Congress, and almost never have overlap in their narrow area of focus with economic expertise. The ones that do are almost invariably law professors, which qualifies them to write the text of legislation but not to design it, if you can see the difference.
As an example, Warren knows little about markets, less about mechanism design and demonstrates her ignorance all the time through her policy proposals. She knows what she wants to accomplish, and they're noble goals, but she doesn't know how to get there.
I don't want the entire Finance and Banking committees in the Senate to be comprised of insiders, but I do want one or two people in the room that can tell the rest of them when something is a really bad idea that won't work from a practical perspective. It's not enough to hear that from experts in public testimony - they need to hear that in closed-doors discussions where decisions are made. It's not realistic to expect that we're going to start electing economics professors that are legitimate experts, so we're stuck with the next-best substitute.