Catholicism, when it's moving into Pagan territory is rather big-tent about Pagan practices. The attitude is "You can keep the festival, just let us Christianize the narrative by removing the pagan gods."
So, you celebrate the solstice as the return of the sun-god? Fine, we'll move Jesus' birthday to that time and we'll celebrate the birth of Christ, Light of the World. Merry Christmas.
You celebrate the coming of the fall harvest and the death of plants in the coming winter as a time when the barrier between the living and dead worlds is at its weakest with spooky stuff? Fine, we'll move a feast remembering All Saints (i.e., All Hallows in old English) in heaven and All Souls (in Purgatory) on those days, now go have fun on All Hallows Eve.
El Día de los Muertos is to a Catholic in Mexico what Halloween is to a Catholic in North America. It's not explicitly worship of a pagan god, so, it's kosher. Not saying that either celebration, when examined more closely, would pass an orthodoxy test; but that, it's tolerated as a cultural tradition.