Yes, this may be interpreted as motivated reasoning, because what I am going to say now just excuses what I have been maintaining...but...
A smallish QB who tends to hold the ball a bit too long NEEDS a superior line. This isn't Brady or Rodgers who can get by with less... it just isn't. Tua NEEDS more time for a couple of years, and maybe forever. The best way to get the game to slow down for him is to give him a top flight line. We've GOT to kick Hunt inside and bring in a top flight RT (whether it is Penei Sewell or someone else). We've GOT to bring in a better Center.
Then... maybe Tua can progress. I am NOT writing him off, I just don't think that bringing in a couple of WRs will do it when he checks down so quickly.