Presumably so long as they don’t stab each other or drown then the standard of the other disciplines evens out and nobody suffers, but the fact is that the majority of them are not capable of riding to what is set as the Olympic level, and they clearly need to do some work or remove the jumping element or revise it in some way.
If as you suggest the level of their skills in all elements is not up to scratch, then MP has no place as an Olympic sport.
Above all, it is the welfare of the horses that matters, and that is what has so shocked the majority of people watching.