There are a lot of reasons why a film can be lousy. Perhaps the worst one is laziness. “The Con is On” (2018) is a limited-release bomb of a caper flick. The caper stinks (stolen loot, a psychopathic Russian, a big jewel, whatever). Uma Thurman looks spectacular and gives the impression of effort as a con artist with a checkered past, but her husband is Tim Roth doing a half-assed Dudley Moore impersonation. Crispin Glover plays himself as a bipolar director. Everyone else sucks and is not worth mentioning, except Parker Posey, who is horrific as a whacked-out movie flunky.