I think people see how gold was struck with DW and DJ so they figure since LW4 was drafted "highest" since Kawhi, that must mean he's going to be a center piece instead of what he probably is, fringe NBA player. That's very well in tune with an 18th pick. A lot of unfair expectations are being placed on an 18th pick in the NBA draft.
That's like expecting your 5th or 6th round picks in the NFL to become All Pros when you should be happy if they crack rotation and stick in the league more than a few seasons. Success would becoming a serviceable starter for either sport.