The ageism is just yet another expression of TRA misogyny; & a demonstration they have no understanding of the considerations raised by previous posters (eg childcare; women’s general treatment in the workplace; the immense [peer] pressure for [female] students & women in some professions to privilege the desires of males over their own needs…).
I mean, if TRAs started crowing that they’re immortal at this point it wouldn’t surprise me, such is the level of knowledge & understanding of human biology routinely demonstrated. (All while, bizarrely, insisting that it’s all very complicated actually, and we’ve got it totally wrong & are embarrassing ourselves 🤨) Taking cross-sex hormones is not a recipe for longevity so when it comes to it, it’s quite possible the grey haired women they see fit to deride will outlive them.
As far as ideas & the belief in them go though - as PPs have noted, Gen A’s are already pushing back against the Zoomers. In England, at least, schools are no longer allowed to teach unmitigated GenderWoo; & the fight is on elsewhere. “I’m being denied life-saving care!” doesn’t play well against people literally dying because they can’t access the care they need; & only gets worse as you unravel “I must have this surgery - but I don’t have a MH problem & there’s no genetic cause… but the drugs & surgery are vital for what definitely is not a choice at all apart from when I say it is”.
There’s no shortage of younger GC women. Admittedly I’m not going to make old bones - or rather, my bones already seem to think they’re old; I always was a precocious brat 😉 I’m in my thirties, so not even that young - but no grey hair. Let’s ignore that about half of it’s fallen out. If/When I do go grey I shall get a blue rinse to confuse The Youth (will need to choose which shades of purple I wear carefully, obviously) & roll riot.
It is sex that is the basis of women’s oppression, not gender. Some women obviously experience oppression on other axes - addressing that is what intersectional feminism is meant to be about; not about centring male people who “identify as” women. Humans cannot change sex. There will always be more women to pass the light.