“Well, it was the third use of papal infallibility.”
No. You’re - not surprisingly - confusing two different things. The authority behind the decree (papal infallibility) is not the same thing as the Assumption (the teaching). The Assumption is not the decree. Papal Infallibility is not the Assumption. The teaching existed BEFORE the decree. Thus, the importance of the dogma or teaching rests not on the decree or its perceived importance for papal infallibility but in relation to the totality of the Church’s doctrines. And by that scale, the Assumption is very small.
“How does a catholic not know this??”
The correct question is: How does an anti-Catholic confuse the actual doctrine of the Assumption with the authority (papal infallibility) underlining the decree it is in as if they are one and the same when they are not?
Again, are these two things the same:
1) Papal infallibility
2) Assumption of Mary
The answer is no. The two are linked in that decree for the pope DEFINED the parameters of the Assumption, but the Assumption of Mary itself is still just the Assumption of Mary itself. It has not become Papal Infallibility, nor has Papal Infallibility become the Assumption of Mary.
I can’t believe I have to explain to you that these two things are different.
You asked how important was the Assumption of Mary. I replied it was the third time the pope had spoken ex-cathedra.
Sure sounds pretty important for the pope to do this. Interesting that the ex-cathedra statements primarily deal with Mary.