I caught the premiere recently of a new sketch comedy show, Thank God You're Here. The show promises antic, improv-style comedy. They don't even have a script! You never know what's going to happen!!

Well, they don't quite deliver on the promise.

Maybe the viewers don't know what's going to happen, but the players certainly have a good idea. The premise involves each of four guest stars, mostly known for their comedy work, being dropped into their own sketch, for which they've been provided no script. There is a rep company on the show, apparently experienced improv players, who populate each of the scenes and drive it with a script, or perhaps a sequence of set-ups.
The effect is that any attempt by the guest star to take the sketch off in a new direction is thwarted by the other players in the sketch, who keep driving it back to the pre-defined setups.

This show is inevitably going to be compared to Whose Line Is It Anyway? despite the fact that they're fundamentally different shows.
As tedious as the American version of Whose Line was, at least it had the veneer of invention. The scenes were treading ground the same players had trodden many times before, so the originality was missing after a while, but it was much closer to real improv than this show is. In Thank God You're Here, no matter how good the guest star is, they're going to be limited by the script the other players are using.

This may explain why Jennifer Coolidge's segment went so badly in the episode that I saw. She was a beauty contest entrant being interviewed. Ms. Coolidge is a veteran of improv comedy, so I was waiting for her scene to take off, but I think she felt particularly limited by the format, and it never went anywhere.

This show violates one of the primary rules of improv, which even a layman like me knows is "Yes, and..."
The players in a real improv scene build it by stacking ideas on top of each other. The premise here requires all the players except one to make sure the ideas stay unstacked.
It may be unique, but that doesn't make it a good show.

David Alan Grier is the host, who gives tedious post-mortems of each scene. Dave Foley is the "judge", who determines the "winning" guest star a la Whose Line. Foley may have the most thankless job of all, as he's required to recall the best lines given by the guest star after each scene.
Maybe if Grier and Foley were in the scenes, it'd be a better show.