This is kind of hard to really say. I don't think any team needs three WRs like we have, plus a TE like Kmet. It's just too hard to optimize them all and I honestly think it's hard, as a weapon, to always give your best when you're less and less likely to see the ball on any given play. So that said, they probably don't play as good as they would if they were being fed the ball constantly.
Also, in a year, Rome will uptick in snaps and targets. He also should make a bigger leap in his own skillset with a year in the NFL under his belt. I totally get what you're saying. Losing a player like Keenan isn't just a "whatever" thing. But, as you imply, he's not been a superstar for us. Whatever reason... old... rookie QB... chemistry... whatever. Either way, I don't think the offense would look any worse with the improvement of Caleb and Rome, plus the familiarity of all the guys with each other (including Moore and Kmet).