Four years into the Seager deal and I think it's been worth it overall. When he's healthy he's one of the best shortstops in baseball. The World Series MVP alone justified the contract for a lot of fans.
The concern is always health with him. He's missed 30+ games in two of the four seasons and when he's out the lineup has a massive hole. You can't just replace that bat off the bench.
At $32.5M a year he needs to be an All-Star caliber player and some years he is, some years the injuries drag his numbers down. That's the gamble with any mega contract.
I'd make the deal again. Before Seager we couldn't attract free agents like that. He changed the perception of the Rangers as a destination.
The defensive decline is real and needs to be monitored. A move to third base in the next 2-3 years seems inevitable. His bat will play anywhere but shortstop requires range he may not have at 34-35.