Bad example, as most pizzas _are_ pretty similar. And in my opinion the best pizzas are not too different from average pizzas. And yes, I had a lot of pizzas in my life, in Naples and elsewhere.
What I mean is: when an inexperienced person compares a scallion pancake to a pizza, or compares a scallion pancake to a taco, the two foods are obviously very different. But when an inexperienced person compares a mediocre scallion pancake to a great one, eaten on different days, it may be hard to remember the differences.
Likewise, someone has rarely eaten pizza might consider a good Neapolitan pizza to be broadly similar to a Domino's pizza, whereas someone who has pizza all the time will notice many differences between the two.