If you look at recent B&R explanations, Wotc has moved away from the term "interaction" to the term "counterplay".
In the banning of Aetherworks Marvel, Aaron Forsythe says,
The best games of Magic are ones that involve counterplay on both sides.
Now this is still somewhat subjective, but I think it is a better descriptor of what games of Magic should be like than "interactivity". It gets past the argument that "prison pieces are interactive, just not on the stack". It gets past the false dichotomy of "is there any difference between locking an opponent out and countering every spell they play?" (both are undesirable play patterns). It means both players should make relevant decisions in a game of Magic, beyond whether or not to mulligan to find Force of Will or "relevant hate piece X". Now eliminating broken plays isn't the point of Vintage - however, reducing or minimizing them is a reasonable goal. It's what gives me pause when it comes to unrestricting potentially broken cards like Fastbond or restricting cheap interactive cards like Mental misstep.