I've accepted it's never going to happen at this point. The guy is built like Jarome Iginla and has a similar toolset (minus maybe the elite shot) and should be an absolute horse down low and a nightmare to opposing defenders, but it just isn't in him. He wants to be a skill transition guy and at this point 6 years into his career that's never going to change.
I think he's nervous about playing along the wall because he knows there's no defensive acumen on his line. That, and he's getting hammered with the toughest defensive assignments possible, so he naturally plays it very conservative.
Would love to see Horvat with a reasonable center (Gaudette being the best option on the team right now, but not an ideal fit), playing regular second line minutes as a winger himself. Have always thought he could have a Taylor Hall like effect as a dominant, play driving north south LW.
But if Horvat stays as a center, I don't think his wingers are the main problem. This is the Mason Raymond thing all over again - people drastically over estimate what a reasonable second line winger should look like. He just needs a real third line center behind him capable of playing top matchups (or Pettersson taking harder minutes). If he had that, along with Pearson and Boeser/Toffoli as his wingers, that's pretty solid.