My family members served this nation in Europe fighting the Nazis and damn near lost their lives doing so don't think you're talking to a neophyte here.
Elaborating more on the concept of nationhood of the East Slavs — the history goes that in the 8th century they invited the Varangian (Nordic) Rus to rule over them. The Rus/Rurikid dynasty became slavicized over 4 generations and then that was cemented when the ruler converted to Christianity.
However, the East Slavs, formed into the “confederation of Kyivan Rus” were not a nation - rather a sprachsbund —> just as “Germania” was.
The South Slavs got a sense of nationhood under the Turkic Bulgars (the Croats/Serbs didn’t get it until later in the 9th century), the West Slavs got a sense of nationhood under the Bohemian and then Piast kings. But I digress.
The East Slavs - whether under Muscowy or Warsaw/Krakow didn’t have a defined sense of nationhood until the late 1700s to the late 1800s. This isn’t unusual - the rise of nationalism came at the same period. Before that, a person from Kyiv said “I’m a Kyivian”, etc. - local sentiments.
Moscow tried to Russify the Belarus and the Red Rus (Ukrainians) in the 1800s and could have succeeded if not for WWI. The creation of “communism in one country” under Stalin pushed Russification, but created the SSRs.
In 1991 the SSRs became independent countries, but Tatarstan, Chechnya did not.
Moscow COULD have ensured that the Ukrainians ‘became’ muscowites, just as the folks from Turin made most Italians speak the Turin dialect and become Italian.
But Putin’s invasions of 2014 and 2022 have invigorated the sense of “Ukrainian nationality” by giving them an “other”/