Almost every movie based on a Saturday Night Live sketch is horrible. Some are better than others, as do some have cult followings, but by and large, they're not that funny. You can't make a movie based on a sketch. They're different beasts using different tools.
Movies need characters. Characters are full people. They are whole, three-dimensional, fleshed-out people. What you see in comedy sketches are caricatures. Those are absurd, cartoonish, inhuman people.
The main character from It's Pat is one-dimensional. It is an androgynous person whose gender people try to guess, but get frustrated when their indirect questions get unhelpful answers. It was funny enough for people to enjoy the several sketches made. But when it was made into a movie, it was a miserable failure.
Pat is not a full person. Pat is a joke. Trying to go from 5 minutes worth of air time to 77 minutes worth of screen time meant creating a lot of scenes that didn't fit and a lot of characterization that undermined what the audience was used to. When the movie did show the classic Pat jokes, they ended up giving too much of them, and the context (being part of a story instead of being a random sketch that ends as abruptly as it starts) affects the reception.
Caricatures are not bad. They are different. Caricatures are useful when you want to tell a joke. They're useful when you want to illustrate a point. They're useful when you need a generic human body of little-to-no importance. They are not useful when you are trying to tell a story about people.
Characters are also tools. There are times when you really do want fully-realized people. There are times when that level of effort would be wasted (like making sketch comedy).
Know what you need, whether it be characters or caricatures. Then use them.