Teams are following that Fangio blueprint how to slow down this offense, they aren't blitzing Dak and playing extra men in coverage. The Jets/Cardinals use this type of scheme as do the Eagles/Dolphins later on. The way to beat it is to run the football against light boxes and take the underneath passes to the sidelines. Look what happened to Josh Allen against the Jets when he tried to take deep shots against that type of defense. Force the defensive to get out of that type of coverage and things will open up.
Should they attempt more down the field shots? Absolutely, but it has to be under the right coverage, makes zero sense if a corner has over the top help. Last week, Dak did hit Lamb for a long TD when they saw man coverage.
As for the red zone, in my opinion, it is a combination of several things: very conservative play calling, poor execution (I can remember several instances, Pollard running into Dak, Hendershot taking the wrong angle, Schoon dropping a pass, Dak's inaccuracy with the fade routes, etc.), inability to run the football and Dak not using his legs enough. I believe with more reps, they should get better, also with better competition, MM is going to have to get more aggressive down there.