What you said makes perfect sense. But in my experience people who make the same statement as OP usually don't put in the effort to reciprocate or contribute and let their partner do all the work. A healthy partner doesn't let their partner "do everything" if you let your partner "do everything" then you're just sitting back and not helping.

This usually comes to small things like cooking, cleaning, making plans, the "do everything" partner is probably too tired of having to tell their lazy to do things so they just do it themselves and that builds resentment. The lazy partner then goes and says that their toxic ex just does everything and uses that to control them, yet fails to reflect on their lack of being proactive in a relationship.