I don't question that the effect is there. I just wonder if it isn't a side effect of some other (not understood) aspect of the universe rather than the result

I don't question that the effect is there. I just wonder if it isn't a side effect of some other (not understood) aspect of the universe rather than the result of the behaviour of some particle. To illustrate, gravity per se doesn't exist, it's the outcome of the bending of space towards mass. So it's effect is real but it's not because some sort of gravitional particle is acting.