Marxists, following Lenin, define imperialism as the monopoly of finance capital. Not as a synonym for ‘conquest’, ‘annexation’, ‘empire’ (not that I’m saying all three necessarily apply to Russia in Ukraine—a conclusion on that isn’t relevant, here).
When US (Anglo-European) finance capital dominates the world through the IMF, World Bank, WTO, and petrodollar, supported by a network of however many hundreds of military bases, all paid for by it’s vassals and enemies due to said dominance, there’s little to no room for anyone else to even consider being imperialist.
We can discuss that if you like. I’ll likely need others to chip in. I’m not proposing that I have all the answers. It’s not something with a clear answer. But we can’t have the debate at all unless we agree on common definitions and frames of reference. Otherwise it feels as though liberals simply do not understand what’s being said. It’s just talking past one another, where one side has a coherent definition and framework and the other side… doesn’t.
I’ll let you decide whether you can honestly say you have a theoretically sound concept of imperialism depending on how much dedicated literature on imperialism you’ve read.