There's a study that often gets shared around, purportedly "Debunking the Myth of the Young Entrepreneur", showing data that most successful startup founders start their companies in their mid-to-late 40s, including tech/social media companies.
It depends a lot on how you qualify and categorise founders, companies and "successful", but of course you can understand why it can be somewhat truthful: people in their 40s have had 2-3 decades to build up experience, networks and a track record, making it much easier to build a team and attract investors and initial customers. I'm sure almost all of these founders in their 40s have had at least some partial success in their past.
So it still affirms that it's best to start as young as possible, allowing time to experiment with ideas, markets, co-founders, etc. I've seen plenty of founders bounce from one-to-another-to-another startup from their 20s to their 40s, each one being vastly more successful than the last.
But as you point out there are still all kinds of opportunities to build new products to address needs that are overlooked by younger founders, so you should absolutely go for it if you're inspired.
I feel the same as you about being less interested in "unicorn"-scale success after 40; as you mature, have kids, experience illness in your family and become more observant of problems in different segments of society, you become much more focused on just providing well for your family and doing some good for the world than having to be some kind of all-conquering hero.
If you want to connect privately to talk more about what kind of company you want to build and how best to go about it, feel free to get in touch (email in bio).