It's not same as separatism. It was similar to fall of other empires.
Take Finland: it gained independence in much the same circumstances as Baltic states. The only difference was that USSR was not able to fully occupy it in 1940. That's it, there is no other reason an average Russian would scoff at Balts and respect Finland than getting a bloody nose there once.
So I call bullshit any attempts to paint things black and white here.
It was not officially recognized as such by anyone, but de facto it was very much a state, and their goal was to maintain that de facto sovereignty.
Poland was established in 966, to lose independence in 1795, to regain it in 1918.
Hungary existed since 895, then merged with Austria (at least in theory as equals, not subjects).
They are nothing like, say, Kosovo which was created 10 years ago by arbitrary UN decision, for no good reason.
Russian Federation ≠ Russian Empire (doesn't exist) ≠ Russia (now Ukraine) ≠ town of Russia (now Old Russa).
BTW. Romania ≠ Rome (now Italy).
Slavic people of Russia/Русь are called "Rusyns/русины" (y as in lynx), literally: "they are Rus`", or "Russish/руські", literally: "belongs to Rus`". Name "Rusyns" was popular in Habsburg Monarchy, while name "Russish" was popular in Russian Empire.
People of Russian Federation are called "Russish/руские", literally: "belongs to Rus`", or "Rossiiane/россияне", literaly: People of Russia/Россия, "Russish" means here believers of Russian Church, mostly Tatars, Erzan`, Mordva, and many other peoples, known as "Russificated peoples/обрусевшие народы".
So, Ukrainians are not "real Russians". Real Russians are assimilated and now are called Ukrainians, Belorussians, Cossacks, Russians, Lithuanians, etc.
Or perhaps, are you saying that the Russian empire isn't truly Russian because the Romanovs were German?
I get what you're saying about country boundaries and composition changing over time, but it seems like a stretch to call Ukraine the true Russia.
880-1240 — Russia - Russia, Русь, modern name: Kievan Rus` (to avoid confusion with Russian Empire), now: Ukraine. Built on remnants of eastern part of Volynnia (Free People) kingdom (now: Volyn` region of Ukraine). Rus`-sia means "Rus` there/this" in Slavic, so "-sia" suffix is dropped in Slavic languages, thus Russia transformed into Rus` (BTW: s(с) and s`(сь) are different consonants). In Western Europe traditional name was used: Russia. They used Eastern Slavic Languages.
Then Russia fall apart into 1) Red Russia, or Ruthenia (Rose People Land), now: Western Ukraine, 2) White Russia, or White Ruthenia, now: Belarus`, 3) Black Russia or Black Ruthenia, now: Grodno region of Belarus`, 4) Carphatian Russia or Carpathian Ruthenia, now: Zakarpattia, western part of Western Ukraine.
1721-1917 — Petro I conquered Russia, so he got title "Emperor of All Russia" (Царь всея Руси). Then Catherine II renamed Moscow kingdom into "All Russia Empire" (Всероссийская Империя), which then simplified to Russian Empire(Российская Империя), or just Russia (Россия).
So Russia can mean Russia/Русся (<541), Rus`/Русь (880-1240), Red, White, Black Rus`, or Russian Empire/Российская Империя (1721-1917).