That's the thing though, the number of things to try is unlimited, there is a large opportunity cost to really trying pretty much anything, and it's not at all clear a priori which things will be worth it.
That opportunity cost is much lower than we all might think.
If it is interesting, that right there is often reason to try it.
Also, things connect in surprising ways.
The real opportunity cost lies in not doing.
People say that they "don't want to invest a decade in something", but fail to grasp that they are invested a decade in something (perhaps watching youtube) -- regardless if they decide to focus it or not.