Improv: yes and no
A newbie can learn a lot from openers, whereas an 'experienced' player hits a curb after a certain point.
As an answer; no, improv. isn't always the best idea. Having something which pushes away the learning, and forces certain views upon those wishing to join, isn't the best idea.
'Stupid' openers =/= fun/supposed fairplay, hence shouldn't be welcome as a primary form of gameplay.

Comebacks: = "fairplay"
Differentiating winning from sportsmanship/fun.