The EU won’t let him in for many years if not ever. Ukraine can apply like Turkey with similar results. Every member of the EU must approve the entry of a new member. Various criteria must be met for entry. Ukraine is a poor country, which means huge payments by the EU to Ukraine to upgrade their infrastructure, e.g., roads, airports, mass transit, etc.
I was living in Greece when they finally got admitted to the EU. It was a bonanza for them.
The EU has that already, with almost 3 million Ukrainians now inside the EU.
The $300 billion in seized Russian assets could provide ample contracts to European firms rebuilding Ukraine.