We are kind of locked into what we have. A single digit percentage of House races are ever contested. The vast majority of House districts are won by the party that already holds them[1].
If 4% or 18 seats were switched four years ago why wouldn't that matter because currently the majority is thin and only a few seats. That could flip in two years. My guess after the gaza comments is more likely than not to switch.
1: https://www.pewresearch.org/short-reads/2024/10/30/decade-af...