I feel like it's not just ageism - software development itself is so big now that it's fractured to the point that there are now strongly opinionated camps that are "stuck in their ways and unable to change - even when faced with evidence to the contrary. "
For example, certain web dev crowds that love (in my very biased opinion) really slow, bloated and/or over complicated tooling to do simple things. But only because they've never ventured outside of their ecosystem to the great beyond and "that's how everyone does it".
The nice thing about the JS ecosystem is there there is no “how everyone does it”.
It’s as if you had Ruby where Rails was only 10% of the market.
Some people say it’s the problem, but I like the egalitarian aspect of it.