In my experience, canned pineapple has a very tinny taste and you taste more of the can than fruit. Cooking that just causes the can taste to seep into the sauce and cheese so your pizza tastes like sweetened aluminum. If you're lucky the can taste isn't quite as prevalent but still not as clean tasting as freshly cut pineapple.
Microwaved, frozen, canned pineapple is the most revolting combination of words I've seen in a while, thanks.
Flavourless sugared mush.