There is ageism for sure. That said, I've probably isolated myself from a lot of it because if a company boasts (as often happens at "work at a startup", etc type events) "we work hard, we play hard", "we are a family" - no. Tell me about what you are building, what you intend to deliver and how you are doing it. What one does in their private life is up to them and should not be tied to corporate culture. If the team isn't experienced and has to work more to achieve commitments - that is a management / hiring issue.

I will certainly expand contributions as needed to help make things successful, but I will not give up my own life to backfill for poor management or hires - did that multiple times and doesn't gain you anything.

That said, making sure junior members are set up for success and get help and mentoring and guidance needed is part of being a senior member. For me, that is part of my calculation when determining timelines and deliverables.