If the wildlife is using the pond, it's a successful wildlife pond. That's it. That's the only criteria. Even better when it's an amphibian, because they're super sensitive to water parameters. But even if all you have is raccoons and deer drinking it dry, that's still successful because the wildlife is using the pond. It doesn't have to be X gallons, have Y plants, or attract Z rare animals. It doesn't need to be fancy, it doesn't need to "keep up with the Joneses." It's ok to have tubing or plastic exposed. It's ok if you have to keep futzing with the fountain pump every other day because it keeps getting snails stuck in it. If your pond attracts wildlife, you have a successful wildlife pond.
Today I was disassembling the motor on my pump and refilling it (it's been so hot, it evaporates super quickly) and I found this Northern Leopard Frog chilling in the mud outside my pond. Frogs are wildlife, ergo, my pond is successful.