In the playoffs the difference has been even more pronounced as Simmons has shrunk from the moment and Horford has shined. I can't imagine many people share Moranis' view...
I suspect a lot of people still share the view that Simmons is a "better" player despite the evidence of this series. Simmons after all plays a more exciting style and you can make excuses for a bad performance in a game or two of a series.
As for the difference between "talent" and "better," I guess the way I look at it is that "talent" is what a player seems capable of doing based on their physical abilities and demonstrable skills, whereas "better" is about how well they actually play.
Russell Westbrook, for example, is clearly one of the most talented players in the league, but his actual game impact doesn't measure up to his talent, in my opinion, because he has a compulsion to play a certain way that prevents his teammates from being fully involved and results in his scoring being fairly inefficient.
Anyway, this is all semantics. The lines are what they are because that's what Vegas thinks will get them the most money. Respect has nothing to do with it, except insofar as it suggests Vegas thinks the betting public doesn't respect the Celtics.