Yes, you can make players pre-plan. You nudge them.

No amount of nudging will make some players do anything. Some players are obstinate and frankly not very good, but honestly the solution to "this player won't stop looking at their phone and their turns take forever" may be to remove them from the group.

Why does it matter how much time everyone takes?

I don't want to wait 5 minutes for someone to dither and dither and finally decide "I attack"