I'd love to hear a couple examples of which "expert opinions" you've disproven for yourself and where you acquired the supporting evidence.
I have one that's related to nutrition. But what's the point if you don't do it yourself, how will you know if I'm right?
Still, an expert, by definition is just someone that has "comprehensive and authoritative knowledge of a subject." You could argue that as soon as you've acquired enough knowledge on a subject to form an accurate opinion, you have yourself become an expert.
Although I'm guessing when you're referring to "experts" you mean "establishment experts." For example, your average doctor whose spent decades studying medicine as opposed to your online research on how to best treat/prevent a certain ailment (you didn't provide an example so I am just referring a fairly common one). What's the difference between your expertise and theirs? On one hand, they have decades worth of rigorous academic study and personal experience over you, on the other hand, you may have a "fresher" perspective that may be devoid of certain institutional biases. I would just strive to stay humble.
Not quite. It's observation of the world around you. It doesn't preclude experts' opinions, it takes them into account. Reinventing the wheel isn't the goal of science. The goal is to understand why a circle might be the best shape for rolling and under what circumstances it might not be.
More specific to current times, ignoring the advice of epidemiologists with respect to masks and social distancing is proving to be costly in life and economy.
"In my experience, whenever I have to rely on an expert opinion I usually feel bad later when I acquire more knowledge in the area myself, as those opinions are almost always wrong."
Care to share a specific example from your life?