Main problem with the Seville (aside from being powered by a murderer's row of garbage drivetrains, but it's not like the Imperial was any better) is that it looks like two different cars. Everything in front of the B-Pillar just looks almost identical to the original Seville, before that fussy character line plunges into the trunk area. Now that was sort of a problem with Sheer Look GM in general following the original Seville and it's not nearly as bad as when the awful subsequent generation looked nearly identical to the Grand Am; but the end result might as well be a Parisienne that someone grafted a Zimmer-esque mess on the back of it. The Imperial in comparison is a very 70s folding paper reinterpretation of the styling they were both aping, and from some angles the Imperial even looks like some sort of... bizarro American version of the Aston Lagonda. The main letdown for it stylistically is that the wheel and tire diameter are both much too small and the track too narrow when all three are about perfect on the Seville.
Cadillac didn't commit fully to the look and Chrysler did. Lincoln seemingly got cold feet when they saw the thud the other two hit the market with. I think the Seville would have worked much better if it looked like an Eldorado sedan with a bustleback.