Earlier quoted context omitted.
> I am a Taiwanese millienial and I am deeply offended by this comment. Why would you say that the claim is understandable? ? Taiwan has been an independent democratic country with its own military, economy, culture, government, rules of law, and international relations for over 50 years. Doesn't this answer your own question? 50 years are nothing in historical terms.
By that logic, you could say the same for any country that has gotten its independence recently (say, Singapore)..
So, if those places had historical and cultural ties with other nations that go way back (like Chinese and Taiwanese people have), then yes, a recent split might not mean much for the legitimacy of a new country.
If those places were merely occupied for centuries/millennia and "gotten their independence" then no.
Heck, colonial powers designed and build states based on all kind of splits in existing peoples to "divide and conquer" them. Statehood comes and go, actual historical and national cultural ties are what's long lasting.