Here are some graphs to show the GOP problem with demographics.
First the party affiliation by cohort from April 2023 https://www.statista.com/statistics/319068/party-identification-in-the-united-states-by-generation/
Next is the number of people voting age by cohort from Pew in 2018 so realize it is worse now for the Boomers and Silent. It's been 5 years since then and the youngest silent generation is 95 and most of them are about as functional as Diane Feinstein. The youngest Boomers are now 59 and the oldest are 77. Their curve is getting ready to start matching the Silent's as the Gen Z picks up steam. (Yes, I edited the chart to reflect 2023 data. *The source I used for current data says there are 65M Gen X)
https://www.pewresearch.org/short-reads/2018/04/03/millennials-approach-baby-boomers-as-largest-generation-in-u-s-electorate/
The net effect is that the most MAGA generations (+3 to +4%) are getting replaced with the most Dem generations (+6 to +14%)
But even then it's all about turnout because as we learned in the mid-terms, turnout matters. I'd argue that Republicans in 2022 were buoyed by Trump not being on the ballot.
https://www.pewresearch.org/politics/2023/07/12/republican-gains-in-2022-midterms-driven-mostly-by-turnout-advantage/