That it was a team effort? The defence surrendered at least a 100 passer rating in every one of those games, that should tell you something.
The Dolphins played the 6th toughest defensive DVOA schedule, with backup OL taking 44% of all snaps yet their QB was still ranked top 5 in every QB metric, that should tell you something.
I know Tua wasn't great at the end of the season, he stank the place up there is no getting away from that. There were also extenuating circumstances that are not excuses, they actually apply. The interior of the OL by that point was the worst in the league, Hill was in a walking boot between games, Waddle missed 2 games, Mostert missed 2 games. People can stick their fingers in their ears and shout "nah, nah, I'm not listening, the QB has to carry the team" but that's not reality.
I'm just saying that after the last 29 regular season games when your QB is ranked top 5 in everything you need to re-sign him, give yourself another 2 or 3 year window and see what happens.