system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why doesn't the Ukrainian president want to join the EU?

Bonus points for also being able to tell me why Ukraine should join the EU.
gpt
Any state that joins the EU eliminates all economic barriers between itself and all other member states, and these states are allowed to trade freely with one another.

Since Ukraine's economy is weak and its industries are underdeveloped, elimination of tariff duties would result in Ukraine's infant markets being strangled by the unrestricted flow of European products - Ukrainian industries would not be able to handle the competition. It is thus not in Ukraine's best interests to join the organization.

Many young Ukrainians think that once their country joins the EU, the standards of living will automatically increase to match those of more developed Western European countries (which joined the EU once their economies were already developed enough to handle foreign competition).  

The "core" EU states (France, Belgium, Netherlands, Germany) want Ukraine to join because it would provide more tariff-free markets for their own goods.