The problem with the liberal definition is that it’s meant to erase capitalism from its natural, systemic compulsion towards imperialism, making it more of a policy choice. The Marxist understanding of imperialism is deeper and more accurate. You can think of the liberal definition as overly simplistic, broad, vague, and with no analysis of why countries become empires, while the Marxist understanding is deeper, more complex, more observable, and explains why some countries become empires (and thus gain massive amounts of wealth from their neocolonies), and their neocolonies remain underdeveloped.
The problem with the liberal definition is that it’s meant to erase capitalism from its natural, systemic compulsion towards imperialism, making it more of a policy choice. The Marxist understanding of imperialism is deeper and more accurate. You can think of the liberal definition as overly simplistic, broad, vague, and with no analysis of why countries become empires, while the Marxist understanding is deeper, more complex, more observable, and explains why some countries become empires (and thus gain massive amounts of wealth from their neocolonies), and their neocolonies remain underdeveloped.