Yes, the record did nosedive into B.o.B.-esque cheese in the second half, but the front end contained some of Wiz's strongest material- ' The Race', 'Hopes and Dreams', 'On My Level'. (See: Devin the Dude.) Also, Rolling Papers was actually pretty good. The list of cannabis-obsessed MCs is long and you don't have to look far to find a Wiz precursor. For one, while Kush and Orange Juice did crystallize the Taylor Gang aesthetic and help trailblaze the mixtape-to-commercial-success model for others, Khalifa was hardly the first guy to leisurely rap about weed. There are a few logical flaws in this argument. Taylor Allderdice, named for Khalifa's high school, is the rapper attempting to reclaim what he sees as his. Concurrent with this were other artists- from psychedelic producers like Spaceghostpurpp to au courant rap crews like A$AP and Main Attraktionz, basically the whole 'cloud rap' or 'trillwave' movement, whatever you want to call it- who had since ran with a similar style.
The gist was that Khalifa had gone too far into pop-rap with his major label debut and sacrificed the kicked-back stoner vibe that first got him wide attention.