John Horgan is a long established and excellent science writer, and given that he's commenting on philosophical issues here as much as anything, I don't agree his difficulty with some mathematical elements of the subject - which he's gracious enough to commit to learning, and humble enough to admit to struggling with - affects his point, which isn't without merit.

But can you call a theory true if no one understands it? A century after inventing quantum mechanics, physicists still squabble over what, exactly, it tells us about reality.

I think his question is a little loaded - it's a cliché that "nobody understands it", and I'm sure there are physicists who would bridle a little at that being true.

His following claim (disputes over what it tells us) - while true - is not quite the same thing, so the argument is flawed in that regard, but not because of a problem learning maths.