I think my reaction was much the same as yours; the sequence starts with much promise but loses momentum, though not quite as much momentum as G.W. Dahlquist's The Glass Books of the Dream Eaters.

I thought the area where it was strongest was its commentary on libertarian hedonism and puritanical self-discipline; neither, it seems to me, in Moorcock's scheme, can exist without the other. The natives of the End of Time might build their menageries and exhibit their collections of other species and (especially) time-travelling humans to each other, but it seemed to me that they were playing to these captives as much as they were to each other.