Many capitalists (myself included) tend to not support corporatism. Capitalism assumes individuals owning smallish businesses. The minute a business becomes large enough to influence the federal government, things get weird and I'm not sure the system works as intended.
Your approach therefore winds up changing the use of the term, to make it more useful for your side of the debate. That's not an especially valid debating tactic...
You have misunderstood. It is not that it is what "capitalism" means because it was what the term was first coined for, its because it was both what the term was first coined for and what it has been used predominantly for since -- both in criticism of that system and other systems sharing its salient features, and in describing (with or without criticisms) actual current systems by how they differ or continue capitalism (both aspects are frequently seen in the descriptions of modern mixed economies.)
The use of "capitalism" for either some other real system that has existed (other than by reference to shared features with the original capitalism) or for some idealized utopian objective that does not exist and has not existed -- whether one in which, as in Marx's Communism, the State has withered away, or one which has a active State with narrowly-circumscribed functions and goals -- is a distinct minority use, and any particular ideal is an even smaller minority use.
I don't believe you that this is inherent to capitalism. Do you have anything this century (21st, not 20th)? An actual citation, not just a claim that this is what they said? Some kind of a study of the degree of cronyism in capitalism, preferably across countries? Something besides just an un-evaluatable claim that depends on the "everybody knows" and the definitions used by unspecified people two centuries ago?