It's not "so vague". It's literally the definition of imperialism.

Imperialism: a state policy or practice of extending a country's power and dominion over other nations or territories. It is primarily achieved through direct territorial conquest, military force, or by gaining heavy political and economic control over the region.

How is that vague? And how does that not describe invading and occupying Ukraine, Georgia, and Chechnya? Or, engaging in political interference campaigns all across Europe and Central Asia?

You can pretend all you want, that these things "didn't happen", or "don't mean what they mean"...but that would be completely disingenuous. Russia is an Imperialist state, which aims to expand its influence and territory, by any means necessary. Whether that's economic influence, political interference, or direct military aggression.

Every single part of that definition applies.