As a kid, growing up, it seemed like math was a solved problem. It'd be very hard to invent something new, because so much has already been done by others. You'd have to get to a very high level, before you could go somewhere where no one has gone before.
In software development, it feels like the opposite situation. There are so many basic things that are currently unsolved and not possible. But they can be made possible with just some effort spent on it.
Here are some open questions that I can think off the top of my head (using the Go language for context):
I'll add more as I run into them.