Reminded of this timeless Carl Sagan quote: "We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology."
Our civilization has attained its complexity by encompassing such knowledge that it would take a million lifetimes to learn all of it. I have made my career learning about technology and learning about science is a great hobby of mine. But I have only the dimmest understanding of even how much there is to know.
In reality people know bits about small bits (think of every person involved in making a mouse back through all materials). And yet without coordination these folks all collaborated to make a mouse. I'm an optimist because people all over the world are making the world better. The rate at which it is happening is picking up, and in general benefiting more and more people. We use communication (including Amazon and Facebook), markets, social movements, regulation etc as feedback loops to find and improve.
The one thing I can guarantee is that there will keep being more to understand, and that as an individual you will keep understanding a smaller and smaller proportion of it.
I enjoy perpectives from Matt Ridley about this (eg The Rational Optimist book) and his Ted talk[2]. A nice tidbit is that King Louis XIV of France had about 500 people preparing meals for him each night. You can go to town and have the same, with far better food and service than he had. By historic standards, we live like royalty, all because we don't understand everything.
[1] https://en.wikipedia.org/wiki/I,_Pencil
[2] https://www.ted.com/talks/matt_ridley_when_ideas_have_sex