That stinks that you didn't get the cheesecake slice of your dreams for your birthday! But I think it's absolutely the right move to skip the slices that weren't living up to your expectations. I am never going to tell myself I can't have cheesecake again, but if I do decide to have it, it is going to be the very best cheesecake I can possibly find!
That said, I agree that our palates can sometimes change a little bit, or at least our physical reaction to what we used to enjoy. I decided on 2 pieces of fun sized Halloween candy this year, picked 2 of my favorites -- a Reese's cup and an Almond Joy. I ate them, and they certainly didn't taste disgusting, but they did not give me that same OMG feeling I used to get eating them. I was expecting after all that time eating no sweets that I would put it in my mouth and go into ecstacy, but really, it was just kinda "eh". Now I know if I kept on eating them, it wouldn't take long before I was craving them like crazy and finding them irresistable again. It was kinda a neat moment for me to realize that I really wasn't missing anything! And I have also noticed how much flavor some of the foods I've been eating actually have. The other day I was just amazed at how flavorful a piece of raw cauliflower is, when before it was just something to put the dip on.
You may have indeed just gotten some crappy cheesecake, but I wouldn't try too many more.