This "Kasich would've won big" meme needs to die.
He would have though.
I highly doubt that. Kasich is a bland, generic career politician, who wouldn't have generated much enthusiasm. He could've picked up Ohio, but that's pretty much it. He would've make Hillary look driven and passionate by comparison.
Trump won because of his "outsider/unconventional" image, that tapped into anti-establishment feelings and political polarization.
Honestly I agree with you mostly
The only people that genuinely enjoy and love Kasich are Establishment hacks who think they're wing is the best thing ever and can easily beat any democrat ever. Maybe Kasich could've flipped OH and maybe IA and FL (The latter is more of a stretch), but anything more is seriously unlikely. He could've lost AZ from how bland he was (A Kasich campaign would basically be Romney 2.0 while Hillary would run a Obama 3.0 campaign against Kasich, likely generating enough enthusiasm to flip AZ to her column).