> Is it mediocre to spend as much time it requires to get a PhD becoming a good pastry chef or carpenter? In the west very likely yes, unless you're an "entrepreneur".
Or, unless you apply your skill into pursuing a bakery career, or a celebrity career (e.g. by running a baking channel on YouTube). Being good at something alone doesn't get you past being perceived as mediocre at best - you have to have an external institution attest for it. PhD, that's easy - the title is itself an attestation. Baking? Proof is in running a successful bakery[0], or in being called a great baker in mass media articles, or in running a popular baking show, etc.
I guess that's implicit in the whole philosophy of "self-improvement" being conditioned on how others see you.
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[0] - However little sense this makes these days; "running business doing X" is 99% about "running business" and 1% about "doing X", and if you want money and control, you have to let other people to "do" X for you.