If you are having sex and your partner isn't unambiguously interested, you need to ask yourself some questions.

Also, people in stable relationships can have non consensual sex. It was legal to rape your wife until like the 90s in parts of the states.

People have agency. They're allowed to choose, of their own free will, to do things they aren't 100% on board with. That includes sex.

Blowing your husband because it wastes less of your time then him trying to woo you or popping a Viagra because your wife is hitting the bong and you know what she's gonna want next aren't ideal but they're facts of some peoples lives.

There's no way you can honestly allege those sorts of things are rape. So how do you justify your redefinition of consent?

Those folks who are not interested can say, "Nah." and if their partner presses the issue that's definitely problematic. A signal of "I'm not interested" should be the end of discussion, there are plenty of tools for folks whose partners aren't in the mood.

That said, there are many folks who aren't enthusiastic about the act itself, but have enthusiasm for the outcome. Many asexual folks I know, for instance, are enthusiastic that they can do something that makes their partners happy, even while not particularly enjoying the act. You are interpreting my definition in only the narrowest possible lens.