I think Creek is probably NBA calibre but in that 350th-500th ranked players in the world, where who is in the NBA is mostly a product of circumstance rather than ability. He's not so good that he must be in the NBA, but he's not worse than say, Bairstow, who just happened to be in the right place at the right time to get a contract.
Landale has looked terrific for the Boomers but he can't guard the way modern bigs are expected to. He can't guard 4s on straight line drives, 5s in the post or the air, and he can't make any useful contribution to guarding a screen. DeMarcus Cousins can't guard screening action, either, but Landale doesn't look like a 20 & 10 guy at the offensive end. The problem is that NBA teams aren't using inferior versions of star bigs as backups, they're going small and playing traditional wings at the 5. So there are fewer opportunities for big men altogether.