There is no “repetition” in Matthew 6:7. It speaks of “babbling” like the pagans, and explains that it is wrong to think that God needs many words. Of course we repeat prayers, — but they are meaningful prayers that remind us of the Holy Gospel, and often cite it directly.
Reciting canned prayers to other dead people is not asking God for anything.
It’s meaningless repetition.
It may feel good, but it accomplishes nothing if not directed to God, making requests or intercession TO HIM.