Deb, here are some answers to some of your questions.
Annuals and perennials were combined for the reason you state: the confusion of annuals with perennials. As for the size of that category (234 entries), it's minimal in comparison with last year's numbers (260 entries in the Annuals category and 333 entries in the Perennials category). The entries in the combined category still included many photos that should have been in four of the new categories (Dahlias, Hibiscuses, Vines, and Foliage) and in the Bulbs or Shrubs categories. If those had been entered in the appropriate categories, the number would have been under 200.
I agree that the Wildlife category is too general. Perhaps it would be best to split it into birds, insects, and animals.
I don't think we need a pet/kid category because those who wish to ignore Muffin and Susie easily can do so even if they're not in a category of their own.
Scenic landscapes could be changed in some way. Those seascapes, sunsets, etc. seem to make their way into four or five categories no matter what we do. I do think it was a good idea to distinguish between public gardens and private gardens, though.
The Macro category continues to be misused even when clarification is provided, so it might be best to drop that category altogether.
In some cases, the same photos were submitted in more than one category because they were moved into a more appropriate category and the contest participants then resubmitted them to the less appropriate categories. It really doesn't happen often enough to be bothersome, however.
Sue addressed your comment about prizes.
The categories usually aren't firmed up prior to the growing season, and I'm not sure that many of our members are motivated by contest categories when they take photos of their gardens.
The categories for specific plants are created on the basis of the numbers of entries of specific plants. Changing them annually would create too many problems. If all of the roses, for instance, had no category of their own and had to be added to the Shrubs and Trees category, that category would be huge and more difficult to judge, and I don't even want to contemplate the size of the Bulbs category if all of the irises and lilies had to be entered in it.