John Candy is like an SNL skit. SNL skits are designed to run maybe 5 minutes. They are quick, concise, and, when they are good, leave you laughing and wanting more. Think about how crappy all the SNL skits they turned in to full length movies. They sucked*. That's not the right format for them. John Candy is like that. It's not intended as a rag on him. How great was Michael Richards as Kramer? It wouldn't work if Kramer had his own show.**
*with due respect to Wayne's World, which I didn't enjoy much and in my mind still fits my point
**sometimes it works, like with Frasier, but then, while Kelsey Grammer the star of that show, he was surrounded by a great cast and bolstered by brilliant writing.