The thread on thoughts over time as to how and when the Ukraine war will end

[President Punxsutawney Phil]

...and a fast track EU application process.

There is no such thing as a fast track EU application process; and if there were, I don't see how Ukraine would qualify for it. In fact, I don't think it is likely that Ukraine will join the EU in the next 20+ years. Regardless of the war, it is a poor and deeply corrupt (Rank 116 in Transparency International's CPI – below the likes of Malawi, Morocco and Peru) country with countless structural flaws and a population large enough to be of serious concern. Given the heated debates about free movement rights and social benefits for 19 million Romanians and 7 million Bulgarians, I honestly fail to see how a majority in the European Council would be happy to have 43+ million Ukrainians joining the club. Especially since this would impose an enormous financial strain on the EU's budget.

Creating the impression that Ukraine may be joining the EU as some sort of reward (for what? for being attacked?) is certainly a nice performative gesture. But once the war is over – or has disappeared from the headlines – the priorities in Brussels will be different ones.

Ukraine joining the EU will certainly take a long time. The benchmarks countries must meet to join the bloc aren't easy to reach.

In my opinion corruption isn't as big of an issue as how poor Ukraine is, to joining the EU. 116th is certainly bad, but it's not that far from other EU candidate countries. North Macedonia 85th, Moldova 91st, Albania and Serbia 101st, and Bosnia and Herzegovina 111th in Transparency International's CPI. 

Meanwhile, Ukraine (and Moldova) are significantly poorer than the Balkan candidate countries. Brussels would be very hesitant to grant membership to such a poor populous country, for the reasons you already mentioned. In fact, the only country to join the EU with a population similar to the size of Ukraine since the fall of communism is Poland. The worst outcome would be a larger Hungary, where an entrenched corrupt Ukrainian political elite uses EU funds for their own enrichment, not having any credible political opposition to keep them in check. The fear of an outcome like that would be another reason why the European Council would be weary of allowing Ukraine into the EU.

2021 GDP per capita, active EU candidate countries (from the World Bank, in USD):

Montenegro:                  $9,466
Sebia:                           $9,230
Bosnia and Herzegovina: $7,143
North Macedonia:           $6,695
Albania:                         $6,493
Moldova:                       $5,231
Ukraine:                        $4,836

What did these numbers look like in 1989?

[President Punxsutawney Phil]

GDP per capita based on the constant of the 2015 USD (using this because looking at GDP per capita based on the current USD vale doesn't adjust for inflation):
                                    
Montenegro (earliest year available 1997): $4,489        2021: $7,351  
Sebia (e.y.a 1995):                                  $2,781         2021: $7,114
Bosnia and Herzegovina: (e.y.a 1994):      $648            2021: $5,893
(1994 was in the middle of the Bosnian War of Independence)
North Macedonia (e.y.a 1990):                 $3,568         2021: $5,287
Albania (1989):                                       $1,809         2021: $4,831
Moldova (e.y.a 1995):                              $1.502         2021: $3,695
Ukraine (1989):                                       $3,330         2021: $2,452
(The GDP per capita decrease in Ukraine happened in the 90s, by 1998 the GDP per capita reached its low point at $1,318.)

Interesting.
Ukraine, IIRC, was among the areas that the Soviets really developed the most (Zaphorizhia, Chernobyl, industry along coastal cities, etc), so it makes sense it was most harmed by the balkanization of the Soviet economic sphere.
Donetsk/Lug-ansk/other coastal cities may as well be the heart of Ukraine's Rust Belt.