Some mathematically inclined LDS may get a little frustrated to do the math on “proxy ordinances”. (Proxy Ordinances are baptisms and other rites performed in the Temples on behalf of the spirits of those who lived and died on Earth without doing them while they were here.) If you do the math, it’s quite possible that LDS aren’t even doing enough proxy ordinances to keep up with the people who are dying each and every day, let alone all those who have gone before throughout time. This would be like bailing water from a leaky boat, but realizing the water is pouring in faster than you’re bailing.
But if we learn anything from proxy ordinances, it’s that the actual person doesn’t even need to be bodily present for the ordinance. They just need to acknowledge the performance of the ordinance at some time or place, and it still counts.
That’s why I wouldn’t be surprised to learn that “proxy ordinances” could count not just for one person, but for whole groups of people. So you could baptize someone “for and on behalf of everyone who lived in the country of Germany from 1749-1773”. Then all those spirits would just need to point to that ordinance and say “Yes, I accept it on my behalf” or “No, I choose not to accept it.”
Maybe we could just do one proxy baptism for the entire human race that died without the chance to be baptized. That’s the wonderful thing about symbolism. It scales really well.