Summer league should be taken for what it is, glorified practice games. You cannot make many decisions on a player based off summer league. Players who thrive in summer league often amount to nothing in the NBA. For example, Jeffery Taylor was All-Summer League Team in 2013 and that same year Ian Clark won the summer league MVP award.
At the same time, there are things that can be learned from summer league. One of the things you want to see is second-year players performing in a dominant fashion. Many will remember that Rudy Gobert was a force to be reckoned with in Las Vegas last year.