Idk, could there be some other big differences between Poland and Ukraine? How easy it is to start a business without being stolen from by gangsters/the government, levels of corruption in public life, Poland receiving hundreds of billions of Euros in subsidies since 2004 (which, while welcome, aren't a free gift and do come with pretty tight strings attached)?
Russia tried being open to the West in the 90's. They got ass-raped by Western bankers for their trouble, and that's why Putin got elected.
It's definitely true that Eastern Europe sucks, but it's not true that being "open to the West" is a guaranteed magic carpet ride to riches or even middle class security. Afghanistan was open to the West for 20 years, money flooded into the place. It's still a shithole. Greece is a full EU member and the best option for young Greeks is to get the fuck out of Greece.
Given that the West is pretty far along the road of replacing its own populations with infinity immigrants willing to work for peanuts (many of them sending remittances back to Poland, lol), aggressively exporting and offshoring industries and jobs, and treading water on historically unprecedented levels of debt, it's not obvious people in the rest of the world will still envy Western standards of living in 2050. They might be jealous of the Chinese instead. But if you were a Ukie or a Russian looking at the situation right now, sure - West is better.
One of the biggest differences was choice of privatization. After fall of communism you needed to somehow give citizens the value of government enterprises, because how else you are going to start market economy?
In Ukraine and Russia each citizen got very small share of governments companies, free to sell and buy as they wish. Soon after that there was group of people who bought those shares, going from house to house, man to man, usually for bargain prices, or abuse this mechanism in any other way. Those people are now oligarchs. In Poland, Czech republic etc. etc. there was other mechanism of privatization. Nobody really got those shares for free, you had to have your own money to bought them. So, this mechanism was less prone to abuse.
This is basically core difference between Poland and Ukraine. All other things like corruption, how easy is to set up company, why Ukrainian politics was so connected to Russian steam from that.
Mind you that every postsoviet country had economics crisis in 90s. Russia, Ukraine, Poland, Czech republic etc. etc. Today's economist agree that so called "shock therapy" wasn't optimal way of establishing changes. Other than that oligarchs problem explains largely Ukraine's policy. Euromaidan wasn't the first revolution in Ukraine. Before that was Orange revolution. There was larger trend of Ukraine being in between Russia and EU. They couldnt get too close to the Russia, because if they would do so Russian oligarchs would swallow up Ukrainian oligarchs without even biting. And they couldnt join the EU, because that would mean oligarchs would lose their position. So there was pattern of large social disapproval, protest, revolution and then back to square one, because core issues with what was wrong in first place weren't or couldn't be changed. You can say what you want about that those protest all were CIA psyops and so on, but I think this is pretty pointless. Even if that's true, it is missing the pictuer of how universal was common Ukrainian hatered for their government. How dissatisfied were with their political situation.
And for the question if Ukraine would be better of joinig Russia or EU, well we have conuterfactual. We have "what if" scenario. Ask Lithuanians, Latvians, Estonians if they would like to live in Russia. Today standards of living in Poland is much higher than in Russia, even though it wasn't the case in 80s. All those Eastern European countries used to be pretty similar under the Iron Curtain. You can complain all you want about "Globohomo", but there is clear cut difference between Poland and Ukraine.