It's immensely important, tactically speaking. Under your idea, if the enemy soldiers were to charge your position, you would have half the amount of time in which to shoot them. People complain enough of run-and-gun tactics, yet this idea would effectively double running speed relative to the defender's ability to engage them.
You think there would be more run and gun in RO2 without zoom?
And that's on top of the fact that it would look ridiculous to anyone who expects the guns to behave realistically. It's particularly bizarre to see this proposed by people who complain that zoom is unrealistic, apparently seeing one unrealistic system (That doesn't let you match what you can do in real-life) as better than another "unrealistic" system (That does).
In what way would it look ridiculous? It would look exactly like when not using zoom in RO2.
That design is what results in things like arthritic old man movement, Parkinson's sway, slow bullets, grenades that throw like bags of cement, SMGs that kick into the ceiling on the second round, and so on. The worst part is, it still doesn't solve the problem, because as long as just one weapon still has any ranged effectiveness at all, you still get the same sedentary behavior that makes movement a huge liability. All of that, just to avoid a simple mechanic that allows a proper simulation to work? How is that a net gain?
I don't see why it would effect movement. Movement doesn't feel that much faster/slower with or without zoom.
A lot of people seem to prefer the Classic weapon behavior than the more realistic weapon behavior in realism.
RO2 doesn't even zoom to realistic levels. For that it would need a lot more zoom. You wouldn't have to change the game as much as you think for it to feel realistic without zoom.