I saw DW 3 times in early 1969 (pretty sure), once in Boston, twice in NYC. I really enjoyed the show, because of Jerry Herman's score and Lansbury's great performance. Every time I saw it, it actually got worse. The first time I saw Each Tomorrow Morning, I thought it was one of the most beautifully staged numbers I had seen to that point (I was only 18 or 19, but I had seen just about every musical in the prior 5 seasons). They completely changed it twice in NYC.
What was wrong: the book was a disaster, the direction got worse over time (can't remember if they changed directors), the choreography also got worse. Other than Lansbury and Jane Connell, the best you could say about the rest of the case was that they were competent. The title number, despite having a great melody, might be the stupidest title song in Broadway history (sorry for the hyperbole, but it was such a stupid declaration).
No, DW is not the best Jerry Herman musical. First, there are the obvious three: Hello Dolly; Mame; and La Cage. Then there is Milk and Honey, a gentle show that was probably his only other hit Herman had. I loved The Grand Tour, which was flawed, but which the audience loved. Then, maybe Dear World, which was actually better than Mack and Mabel, which -- despite a great score -- was a horrible night in the theatre...the audience barely applauded at the end of that one.
Anyone who thinks DW is his best show is entitled to their opinion, but I still feel sorry for them.