It's right there in your first three words, it didn't change so much as you, "grew up". It doesn't have to be technology, you could probably say the same thing

It's right there in your first three words, it didn't change so much as you, "grew up". It doesn't have to be technology, you could probably say the same thing about most things in your life, "I don't know what happened. I used to like hanging out with my friends, riding my bike, listening to music. But then things changed and now I've got a job, a mortgage to worry about and it's all about money and I never have enough time to do the things that I want to do". But you have an internal contradiction. You're nostalgically looking back at a time when you optimistically said, "Wherever I looked at the world's problems, more technology seemed to be the answer" but then say that, "Today's startups are solving the most boring problems imaginable.". More technology is not the answer to most problems and most problems are boring.