Like so many other things, the Mail likes the idea of monarchy, but only in a very nostalgia-tinted, idealised way*. They like having people up there on a pedestal to coo over and admire, but also there as a target for their opprobrium. Just more characters in the Living Soap Opera, same as entertainers, politicians, anyone else in the public eye.
Whil I have little time for the concept of monarchy, I do acknowledge that those born into it are human beings, with real thoughts and feelings. Aside from presiding over things and opening other things, they have little real function, and are indeed damned if the do or don't.
*Like Christmas, many of the trappings of British royalty are a lot more recent (and non-traditionally 'British') than many would acknowledge.