He got hurt vs. Redskins and missed the next game. He had 4 receptions for 134 yards in those first two games and a few big plays...seemed like he might be getting a number of targets each week...but then he got injured, missed the Niners game and never really got back into it much. He's also from a small college, which could also be a factor.
I look for a lot more from him next year after a full offseason with McVay and the offense.
And yes, drawing conclusions on any draft after one year is not advised.