Furthermore, popularity is not a factor in "new".
The evolution of a rifles from the muzzle loading flintlock to the M-16 was nothing more than a series of improvements to the basic design.
And even though they are all still rifles, the changes were inventions because they differed in what had gone before. They weren't just an improvement, they previously didn't exist.
You seem resistant to calling something new because there isn't enough change or difference to qualify calling that something "new". If you wish to twist the meaning of "different" to mean "better" instead of "new", I call that a game of semantics.
The discussion was about inventing something. For something to be considered invented it has to be new, previously unknown, (not necessarily better) markedly different from what went before.
Your chose the topic- rifles.
Muzzle loading musket through to flintlock- they are all still rifles, there is nothing new there. You shoot over a long distance with it (although by definition a rifle is, well rifled)
The inventive part was the different methods of loading, rifling.
Rifling can be considered an invention, it hadn't been done before- new/ different
Paper cartridges over pouring power muzzle loading- different/ new.
Modern bullet- new/different.
Back to the Pizza- No new Pizza was created, just an existing product was improved.
And whether or not you call it (derisively) semantics, the distinction is important. It's up to you whether you use words correctly, or not.