Not exactly. Ex Cathedra declarations are believed to be infallible, but infallibility is thought to reside in the institutional church in the absence of any such Papal decrees. Hence, the Magisterium is said to be infallible, the Councils are said to be infallible, etc.
The problem lies in the etc. For example, Papal Bulls, which were once considered to be dogmatic statements, are now generally ignored altogether.
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