This simply isn't true, at least in regard to millennial voters.
A glut of voters in that age range are actually
increasing their support of democrats, according to Pew Research data and interpretation. In 2002, millennial voters (1981-1996) were 33% democrat, 34% independent and 27% republican. In 2017, they were 35% democrat, 44% independent and 17% republican. Since then, their support of democrats has grown — up to 59%.
This gives democrats a "27- percentage-point advantage" over republicans among millennial voters.
It's nigh-impossible to gauge generation z voters, though. They haven't had a chance to vote in a presidential election, only the midterms.
Yes there are pro-life bents among young people. But scrums of young people also support progressive policies. Millennials
by and large support Medicare for All, Bernie Sanders's healthcare policy.
Two-thirds of the nation supports a federal minimum wage increase (thanks, in part, to millennial voters),
62% support rigorous environmental policy, and, additionally,
raising taxes and
tuition-free public college are on their radar as well.