Blake Bortles isn't, and won't ever be, a competent NFL player. He has above average NFL talent, but he just can't put it together on the field. They need to replace him this offseason, and that starts with the draft. "Sacksonville" won't be picking high due to its insanely talented defense and a few really good offensive players (Fournette, Linder, Norwell, Westbrook/Cole are pretty good). They'll be picking in the 20s, and this is a draft where they won't have to trade up due to a lack of high end QB talent. Also, they don't need Tom Brady--they just need a starting-caliber passer, and I believe that's what Drew Lock brings to the table.
Some have criticized Lock for not having a commanding locker room presence and for being an introvert. He's no Ray Lewis or Drew Brees in that sense. However, his quiet personality is perfect for a team like Jacksonville. They already have a ton of talent in place for Lock to succeed, and as a former 5-star recruit, he's already pretty talented himself. The Jaguars' D provides the leadership in the locker room (Ramsey, Calais Campbell, Telvin Smith, Myles Jack, AJ Bouye, etc.) and Lock has a better skill set and attitude than Bortles. A vocal guy at QB may cause friction in the locker room due to a power struggle within the team. Lock's shy demeanor fits like a puzzle piece on that team.
Maybe David Caldwell, who has proven to be a solid GM, makes the wrong decision and keeps Bortles or unnecessarily trades all the way up for Justin Herbert (who I am not as high on). But in my opinion, the answer to their playoff woes lies at the University of Missouri.