Of course we appreciate the positive effects of standardization. The Roman Empire (over 2 millennia ago) is known to use standardization practices, but in a very limited way. For example, the Roman Empire allowed conquered countries to keep their religion and language. Often it used local people as leaders to self-govern the conquered nation. The Roman Empire provided the people with some standardization: peace, protection, and the ability to trade within the Empire and other economical advantages.
Soviet empire also provided the conquered nations with standardization, but it replaced local religion with Soviet propaganda, nationalized and confiscated property, and enforced the use of Soviet currency, language and other standards. Leadership was also replaced and standardized.
America is very good in standardization. American states enjoy a large standardized market, strong currency, peace within the country, absence of customs between states, universal language, standardized law, freedom of relocation of individuals, and many personal liberties including very liberal religious freedoms. This helps the economy very much.
A great example of voluntary unification and standardization is the recent creation of the European Union. Many countries voluntarily joined the European Union, which provides similar standardization as the United States. Clearly humans, especially in recent times and in more civilized countries are capable of volunteering for standardization, especially because it demonstrates positive results. Practical advantage is a very convincing argument for humans, but it takes time and testing to see how it works in reality. Humans would be unlikely to volunteer for standardization without trying it on a limited scale.
Note that the countries of the European Union standardized only economic principles, but kept their languages, religions, culture and borders. They continue self-governance.
STANDARDIZING GENETICS I would really doubt that modern humans would volunteer for standardization or even change of their genetics. This may change with time, but now it is clearly not an option.
A couple things may open the doors to human genetic modification.