The problem with term limits is that they don't apply to lobbyists. Lobbyists basically writing most of the legislation is already a major problem, and it becomes worse when all the representatives are new to the office.
As you say, it's easy to point to the folks who have been in office forever as being an issue, but there's also staff and lobbyists and other unelected roles that are hard to get rid of the influence of. At the end of the day, someone needs to be the expert, either on the vast array of issues that can come up in national government, or in how to actually do something about those issues.
If a lot of the "real" work is done by the staffers, career government workers, etc then the politician really is the public face and occasionally redirecting the ship. I'd say there is less risk there and more to gain from fresh faces and opinions in that spot, again if that's how the workload shakes out behind the scenes