It's hard to blame the members of the House for being old. It's the rest of us that keep electing the same people over and over.
But, it needs to be stressed that there are structural reasons for this—mainly how seniority works in Congress. And, even tossing out the incumbency biases that voters may have—there are good reasons to have long-term members. It takes time to learn the system and build relationships. Sometimes this can work well—such as when LBJ pulled chits to get the CRA passed, but other times not—where cronyism, nepotism and inertia hamper progress. The question is, how to reform the system to produce better and more equitable governance?
I have to push back on this, though. The House members themselves don't have to keep running for the same office 20+ years, that's their choice. And you can say what you will about us when it comes to primaries but incumbency literally matters. The DCCC/DSC/RNCC/RSC are first and foremost defenders of incumbents, with suitable resources. Parties should have a vested interest in maintaining some turnover for both underperformers and leadership in the legislature. I don't want legislative term limits, but IF that were the only practical method to achieve this end, I would suggest the minimum term limits to a legislative body be 18 years. It would allow more than enough time to develop systems/relationships but discourage stagnation and also dovetails nicely with the proposal of 18yr SCOTUS term limits. But I would much rather parties themselves get better mechanisms for internal turnover.