By relating the facts.
He scored 9 offensive TDs in 2015 being used as both a runner and receiver as a hybrid combo.
In 2016 they used him more as a pure receiver and that was not as effective.
In 2017 they use him more as a runner and that's limited too.
He could still be used in both ways in the hybrid role but it appears that a lot gets in the way of that---Tavon missed a lot of OTAs and training camp so is behind in a lot of respects. Plus McVay does not seem to be interested in that hybrid role--which he is still capable of doing.
Combine what he does in 2017 with what he did in 2016 and you actually have a more dynamic version of 2015.
But again, McVay doesn't seem interested. Which is his right, he did not draft the guy.
Oh yes and to respond to your point, he did fumble a lot as a punt returned in early in 2017. He may be back on punt returns after a bit, he may not.
....