The majority of NFL teams keep looking until they find their #1. That doesn't mean it isn't important, it means they aren't easy to find. It's why the process never ends.
Obviously every team would love to have "a true #1." And the Jags surely covet one as well. But WAY too much is made over the topic - and it's often just used to disparage many very talented receivers being discussed around here.
Until there's a clear cut #1 guy on the roster - there's little point in debating who is and who isn't. Who plays what role (x,y,z) is much, much more relevant, IMO.
Robinson has the skill set and body type to be a very productive x receiver. That's all I am concerned about him doing.