Clearly, the fact that he wants the Deshaun Watson deal plus more is a problem for a lot of teams, especially with the knowledge that the Browns' ownership pissed everybody else off with that deal. But, there are individual reasons.
Let's go down the draft board.
The Panthers -- already traded up to first overall. They're drafting a quarterback and getting him cheap for sure four years.
The Texans -- basically the same as the Panthers.
The Cardinals -- They've got Kyler Murray. They need young players to fix the roster.
The Colts -- they've been down this road of trying to trade for a quarterback too many times now. They're drafting.
The Seahawks -- on paper, this would make some sense; but, Pete Carroll isn't gonna go for it.
The Lions -- they're gonna roll with Goff for another year and build out the roster.
The Raiders -- they're not in a Super Bowl window. Not the time to trade away your rebuilding assets.
The Falcons -- same as the Raiders
The Bears -- they've got Justin Fields. Need more weapons for him.
The Eagles -- made it to the Super Bowl with Hurts. They're sticking with him.
The Titans -- again, pretty sure they're gonna draft a young guy.
The Jets -- looks like they're getting Aaron Rodgers
The Patriots -- no way Bill is giving Jackson that kind of a contract.
The Packers -- they're gonna give Jordan Love a shot.
The Commanders -- eh, this one might make some sense. Most of the desired quarterbacks would have been selected here, and they need a quarterback.
The Steelers -- pretty clearly sticking with Kenny Pickett.
The Bucs -- with what cap space?
The Chargers -- Justin Herbert
The Vikings -- they've gotta give Cousins his last year. Seriously, look at his contract, they couldn't get rid of him if they tried.
The Jaguars -- Trevor Lawrence
The Giants -- could make some sense. Jackson is a clear upgrade from Jones; but, the Giants just have too many holes.
The Cowboys -- Dak and cap issues
The Bills -- Josh Allen
The Bengals -- Joe Burrow
The Saints -- they're in cap hell.
The Chiefs -- goes without saying.
(Teams that don't have a first round pick)
The Dolphins -- could happen. They tried to get Watson. Still, they don't have a first round pick to trade. Also, it stands to reason that they didn't get Watson because they wouldn't pay him what the Browns gave him.
The Rams -- Matthew Stafford
The Broncos -- don't have the picks to make the trade. Probably sticking with Wilson.
The Browns -- already made this deal with Deshaun
The 49ers -- don't have the draft picks. Jackson doesn't fit The offense.
Of course, Jackson is a top five talent. He'd be an upgrade over Kyler Murray, and a huge upgrade over Derek Carr and Jimmy G. He's also a proven commodity unlike the guys entering the draft this year.
But, there's a reason why we talk about Super Bowl windows. A trade for Jackson with probably require three first round picks and some change; and, right after that, the team that makes the trade will have restricted cap space for several years. Namely, it would have to be a team like the Browns, who figures that they're ready to win now, and they just need a quarterback, and they're willing to trade the future for the present.
That doesn't apply to many teams. And, even for the teams that it does apply, you still need a team that's willing to piss off the rest of the league. On top of that, you need a team that's willing to ignore how awfully the Browns regressed this season.