The defense forced 4 turnovers and held one of the top offenses in the NFL to 10 points in the 2nd half. The score was 21-16 going into the 2nd half so while giving up 400+ yards isn't ideal, the defense wasn't as horrible as everyone claims.
Dallas had more yards offensively than TB (451 to 431), had less penalties/penalty yards than TB (8 for 55 vs. 11 for 106), had a +3 in turnover margin, had more offensive plays (77 to 64), and won the time of possession battle (34:27 to 25:33).
However, an area that Dallas failed to best TB in: Red Zone efficiency. Dallas was 1 of 4 in the Red Zone versus TB's 3 of 5 in the Red Zone.
Also keep in mind that TB was leading 21-19 after a a Dallas FG and a Dallas defensive stop......and on 1st and 10 from their own 25 yard line Dak threw an INT which led to a quick TB TD. While Dallas scored a TD immediately after leading to a 28-26 TB lead, the Dallas defense forced TB into a punt on their next possession . Dallas' next possession led to a 3 play 2 yard punting situation. The Dallas defense then forced a TB fumble giving Dallas another chance.
The point is the Dallas defense was stepping up later in the game giving Dallas a chance but ultimately Dallas lost so on to week 2.