That is a tricky question :D
In my opinion it differs per person. Wealthy people their time is more costly, with means they should be more of an investor. Less wealthy people their time is less valuable. Which makes it more important for them to be an earner.

The middle class will have to find a balance between earner and investor, and adjust as they progress in whichever direction they go.

One thing I know for sure, is that nothing lasts forever, and we have no control on certain things in life. So you got to always be prepared to shift gears whenever necessary.