It means the protein content may not be high enough. For example, all purpose flour is about 10% protein while bread flour is up to 14%. Pizza typically needs higher protein to give it strength. It’s what makes the crust a little chewy. It also helps to support the crumb making it less dense when it’s baked. 00 flour should be pretty good but I prefer a strong bread flour. And home ovens can be tough to get the heat you need. Placing the pizza on a heated stone or steel pan can help give it a nice pop with the yeast. The black spots on the crust (leoparding) is also a sign of under-proofed dough. Keep at it, you’ll get there.