Why can't Catholics admit there can be a new Messiah?

Why are Catholics afraid to admit that a new Messiah is possible in this day and age?

It isn’t fear to deny the possibility of a “new Messiah”; it is simply an assertion of fact that Jesus of Nazareth is the one, sole Messiah to the exclusion of the possibility of any others. As you yourself profess to be Catholic, this is something you must admit as well.

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