What sitcoms started on the wrong foot, were retooled in an attempt to improve them, only to end up worse?

I agree about Doris Day, it was never really a good series, started out on the weak side and didn't really improve over the course of it's five seasons. Another thing working against the show is that it hasn't aged well at all, it retains some nostalgia value but that's about it.

The 1st season of Joey Bishop isn't that good, but I think the re-tooling of the format helped the series and the 2nd and 3rd seasons are an improvement over season 1. Then in season 4 the series took a bit of a step backwards again.

Saved by the Bell: The New Class. This show made Saved by the Bell look like Shakespeare. How on earth did this series last seven years?!