I'm still early-ish in my career as a software engineer but currently I'm deriving meaning from pursuing mastery of my craft; trying to get better every day, tackle harder and more advanced problems. For me this pursuit feels meaningful. Most tech jobs are B.S. and you rarely are "helping" the world in any real way. But if you are constantly improving and being challenged you will A) have more fun on a daily basis and feel better about yourself, and B) be much better prepared to eventually execute significant, meaningful changes in the world from a position of expertise and experience. Just my personal outlook / strategy.