> That doesn't actually seem like a huge achievement

Historically, it has been.

> Inflation is the rate of change so if you stop creating as much money out of thin air, then it's not really a surprise that prices don't increase as much

You're confusing money supply and price levels. Inflation measures the latter. You can have constant money supply and stable prices, inflation or deflation. And since most money is privately created, controlling how much money is and isn't created "out of thin air" is actually quite challenging.