https://marvelcinematicuniverse.fandom.com/wiki/Pym_Particles
Tony built Quantum Tunnel for the Time Heist so the intellectual property shouldn't be a problem. They needed everything they had to save the world. But Tony couldn't make more Pym Particles. Why is that? He had samples and access to Hank Pym's knowledge. His intelligence was enough to solve the time travel puzzle. He and others had time to be prepared. He had everything he needed to make more Particles. It's just a replication.
Storywise, it helped Tony and Cap went through more drama. I know that. Let's go back to the capability part.