Ya but you have to defend 5 players. If all 5 players can shoot the 3 like the Mavs showed yesterday then someone like Gobert is in big trouble. Who's going to defend Gobert's man if Gobert stays in the paint?
That's not all on Gobert though. Mavericks, and Jason Kidd said this, they would exploit matchups that they could take advantage of. And this hasn't just been the Jazz's issue for this year, they have struggled with a balanced lineup without Gobert. As in, really good regular season, but when teams go small and spread the court out in the playoffs, especially against a team like the Mavericks (or Clippers, or Rockets a few years ago), who jack up 3s and live on the perimeter with a mobile 4/5, it's going to cause problems.
Jazz went Mitchell, Conley, Clarkson, O'Neale, and Bogi. That's zero perimeter defenders. Maybe O'Neale fits, but Bogi sure as hell doesn't. And that's a 3 guard lineup - Clarkson is long, but skinny. Conley is more offensive but older and not the defender he once was. And Mitchell is a below average defender most trips down the court. You put that 5, which is what Jazz did, against Doncic, Dinwiddie, Brunson, Finney-Smith, and Kleba...that's a problem. Mavs were agile, long, and committed enough to keep their guys infront of them or at least usher them into traffic where Finney-Smith and Kleba could collapse.
Utah didn't construct their bench/team effectively enough for the playoffs and the different matchups they would have seen. And regardless if they saw it or not, they have a huge problem defending when Gobert is out or they are up against a team that goes 5 outside. Danny Ainge is going to be make wholesale changes within the next year, two at most.