I agree with you there. Of course his YAC will improve with better spacing. So, of course, would Durham Smythe's, and everyone else on the team. Gaskin can't make defenders miss, but he had that sensational catch and run against the Raiders in week 16 that would have been a well remembered play in Dolphins lore if the last few minutes of the game hadn't involved two more lead changes including Fitz's throw when his face was sideways.
But what Waddle is simply not good at is making guys miss. And while that's something that I have observed, it's also something that is statistically tracked- I apologize, I don't know where I saw it, I came across that two weeks ago, and remembered it because it confirmed what I thought I was seeing. And noting on the field the last two weeks made me believe that's changed. The stats show that Waddle was like the third worst player or at least third worst receiver in the league at making the first guy miss. While the overall production is influenced by spacing, not making a guy miss- that's just a one on one matchup that he simply is never winning. He catches the ball and then gets brought down by the closest defender almost all the time, whenever that is. I mean, I've seen Devante Parker, who really isn't a YAC guy unless he catches a slant in stride, catch some passes and just sidestep a guy to get 4-5 yards before the next defender gets there. And Waddle just doesn't do that.
The reason why I say the Dolphins missed their eval on him - I mean we've schemed up more routes and plays for him than all our other players combined, partially due to availability, and the stuff we've been running with him really only makes sense when a guy can catch a pass and elude the nearest defender (like bubble screens). The team traded out of the opportunity to draft a guy with a more downfield body type and play style like chase, and clearly they wanted to pair a QB who excels at ball placement on short routes with a guy who they thought could catch the ball and make defenders miss.
It seems like the ability to either elude or evade tacklers is something more predicated on physical skill and ability than something developed over time, like route running and technique, so I don't know if Waddle will ever get drastically better. It's really not uncommon for guys to make a lot of players miss at the college level because they are just faster than everyone else to struggle to get around guys at the next level when suddenly that aren't head and shoulders faster than the competition.