Hey there,
I know this is already an old topic, but I have to express, that I am deeply unhappy with the way this is handled right now.
populate=* should populate everything the way Strapi V3 did it. That means up to 3 levels including dynamic zones, media, relations and nested components.
The new API-Features are great but we definitely need a fast track to get all the data we need (including the 3rd level).
Being able to be selective and giving the REST API almost GraphQL like abilities is nice, but complicating the way to get all data is not a good choice.