I believe in the observational effects of something we call gravity. As to its nature, that is still unknown. GR is one model/theory and it works most of the ti

I believe in the observational effects of something we call gravity. As to its nature, that is still unknown. GR is one model/theory and it works most of the time. But there are observations that do not fit into this model. That is the sticking point - these observation suggest that, though GR is useful, it is seriously flawed. Can we use it, yes. But to believe that it is true, that is something quite different.