Cuba is a liitle bit different case in my oppinion. I do not see problem with Cuban athletes.
We have slightly different situation. There are many diasporas from the Caucasus in Ukraine, so we did not need to find mercenaries.
These diasporas keep their traditions and culture but they are deeply integrated into the life of Ukraine, speak Ukrainian.
For example, Nasibov was born in Azerbaujan, but came to Ukraine (Mykolaiv) in the age of 6.
Zantaraia (judoka) born in Georgia but came to Ukraine because of the war in Georgia. Now he is a politician.
Belenuk is another case - he was born in Kyiv.
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* In my oppinion, the other reason of our problems (and problems of many other countries) is the policy of the IOC. They are reducing and reducing quotas. And the Games are getting more and more elite event. Quotas are going to top powers and and a group of weaker representatives to ensure geographic diversity. The "middle class" is the main victim of this policy. And the result of this policy in a long-term perspective is disastrous for the local sport development. No Olympic quotas means no funds and no young athletes.