No, you shouldn't turn down open shots - any open shot is a good shot, provided it's in the shooter's range. But the worst shot in basketball is one with a foot on the three point arc... lowest points per shot on the court. I never understood guys who took a single dribble to step up and put their heels just past the line - they're not increasing their percentage, and they just gave up the benefit of shooting from distance.
Ideal would be shots from 0-14 feet or so, then 19+. Bigs stepping out and hitting jumpers, guards pulling up for shorter jumpers over shot blockers, outside shooters driving past tight defenders to get a better look... sure. There's just not a lot of call for the 15-19 foot range - better off getting 50% more points for a slight drop in hit rate.
Steph Curry's 2015-16 season was an offensive clinic... and here's his shot chart that season. It's almost exclusively threes and shots in the lane.