Agree/disagree with your view. Actually I think that really exciting, interesting, good history is being written today of an excellenet standard and without the aridity and pompousness that sometimes characterised very valuable contributions 100 years ago, - and that's not just because of the period they were written. The books of some contributors to this forum are egs, as are the "Longitude" genre. The standard offered to the general public today is better than at any time in history. I don't think the average member of the public ever attempted to read (say) Napier or Oman, let alone the other authors cited. These books were for the relatively small class who read "serious' books. Today that group is much, much wider.
The appalling relativism you mention has had its benefit in making writers a lot more aware of alternative views of the same subject, which must be advantageous, while being very destructive in other ways. However, I stick by my belief that more and better history is being written and read today than at any other time.