I just don't know where the data is "for a 6th year QB." I try to lump all QBs in after their second contract and hold them to the same standard. Kyler's clearly better than his fellow sixth-year QBs Daniel Jones, Dwayne Haskins (RIP), and Drew Lock.
He's better than Sam Darnold and Josh Rosen from the 2018 draft class was in their sixth year, but not Baker Mayfield (some will quibble with this), Josh Allen, and Lamar Jackson.
From the 2017 draft class he's better than Mitch Trubisky was in his sixth year, but not Patrick Mahomes. I don't know how much you want to fight about where he compares with Deshaun Watson in his suspension-shortened sixth season, but I fully expect Kyler to be better in his seventh season than Watson was.
From the 2016 draft class Jaren Goff had been traded and was going 3-10-1 with the Lions and passing for fewer than 3300 yards, 19 TDs, and 8 INTs. Carson Wentz had also been traded and was going 9-8 for the Colts on his way to becoming a Journeyman QB. Kyler's way, way better than 2016 first-rounder Paxton Lynch.
From the 2015 draft class, Jamis Winston was starting zero games for the New Orleans Saints in his sixth season, after creating the 30-30 club for TD passes and INTs the previous season with Bruce Arians. Fellow top draft pick Marcus Mariota was also starting zero games in the beginning of his two-year stay in Las Vegas where he'd start zero total games.
I get people being mad that Kyler isn't Lamar, Allen, or Patrick Mahomes. In a lot of ways those are his peers. But he's obviously at or near the top of the next group of guys.
I was simply using 6th year to highlight he's a vet and he's had enough time.
As I said, at core traditional QB skills he's one of the worst in the league.