I personally dont find this idea horrible. First i will point out that i am agnostic, and i dont have a distinct belief weather there is or is not a god, or if there is or is not an afterlife. But i dont want to exist forever, eternity is quite a long time. I just cant see anything being peleasurable if life is eternal, if you exist forever after a while everything loosese meaning. And if there is an afterlife i will be very diasapointed.
Now about hedonism, someone in the coments of the original idea mentione that ife there was no afterlife they would just seek pleasure, and not care at all about other people be a dick to everyone, not sacrifice anything for anyone nd so on. But if ones reason for treating others with compassion is because there is and afterlife in which they will be rewarded, that is not really compassion to begin with. If one is compationate treating people as such is an end in itself for them, no reward should be nessisary.
Another point mentioned was that as eastern philosophy states we are one with the univerese, and we are in fact the universe. This is a pont of view i tend to subscribe to, i came to it through mataphysical analisis rather then religion but that matters little. But if that is the case then we as beings have no identity, we are simply the univeerse conected to all other matter. And if we have no distinct identity then there is likley no eternal concionsess, we simply die our phisical patern disintegrates, and whatever matter that made us up over the course of our life (matter in the body replaces itself all the time so there would be alot of it that was parto of our pattern at some point) just gets redistributed to other paterns.