Pizza once a week is fine but preferably it should be a small amount with salad, rather than a whole large and/or deep pan takeaway pizza.
Different people's idea of pizza will be very different from a health perspective. Some people will have half a smallish frozen pizza with salad and have a meal that is about 500 calories, while others will have a whole large takeaway pizza, which could be over 2000.
There's also the processed meat aspect, which is another health concern. I wanted to buy a pizza in the supermarket the other day, but nearly all of them that weren't plain cheese and tomato were laden with pepperoni or other processed meat.
I love pizza but I don't like chicken on pizza and I don't like any pepperoni or similar processed meat. A bit of ham is OK, but I generally like either tuna, onion and olives or mederteranen veg like peppers, onions, mushrooms and olives.
I wasn't in the mood to start cutting up veg to put on a plain one so didn't bother in the end.