I was willing to subscribe to his criticisms until I reached the following paragraph:
The key with any sequel, whether it’s The Godfather II, The Hangover II, or Indiana Jones & The Temple of Doom, is to think about the promise the original made to the audience, and to deliver on that same promise, in a slightly different way.
All three of those movies (with the possible exception of The Godfather Part II...) don't come close to comparison with the original films. Especially in the case of Hangover Part II and IJ: Temple of Doom, when both of those films are barely shadows of the great films that preceded them.
And, on top of that, I provide counterpoint: Aliens. A film that completely upends the "engine" of its predecessor, and ends up being the superior film. (I note that this is a contentious opinion, however).
I don't think the author was arguing that those sequels were necessarily successful, I think he was just giving examples of how in any genre or level of artistry you should remain true to your purpose.
Also, I think there is a lot more leeway with films than with television. And there's even less leeway with comedies.