Now let's be fair and honest with this statement, given you've positioned it in a way that makes it sound like Jones was holding Smith back instead of this season being career highs for him in receptions, yards, and targets. And even taking into consideration him having his career season, it still ended up being only 34 yards per game. Hardly the game breaking talent you seem to be implying.
Jonnu Smith isn't anything more than a solid, playable tight end, but it's not just about him. Since you brought up yards per game, all but one of the guys they brought from the outside to play with Mac had a decline in yards per game when they had to start catching passes from him. Henry, Smith, Agholor, Parker, JuJu and Gesicki. Some of them had bigger drops in yardage than others but everyone besides Bourne dropped.
The qb has to take a decent amount of the blame for that. Zappe isn't good and probably gets cut but some of these guys showed they at least had a pulse when they made him starter for the rest of the season even if it was just for a game or two. Maybe if their options at qb aren't a noodle arm with bad fundamentals and craps himself under pressure, or a guy who's inaccurate even when under little to no pressure and can only play well for one half of the game, and they can instead find a guy who doesn't suck and has some arm talent, the pass catchers might actually be better than what we think they are.