The author only seems to be bringing up the colour thing as a secondary objection, not that it makes any sense to me. I doubt if EmilyBrontė thought of Heathcliff as black.
The main objection seems to be that the two leads are too glamorous for the roles. However, these people are actors and whether they can make a fist of the parts depends on their ability and the quality of direction. I know Robbie is a fine actor, don't know about Elordi. Why not see if they can do it before whining about them.
There was some comment on social.media thar they didn't seem 'tortured' enough for the roles but agree that should be covered by them acting.
There is a bit of a question of age but that's a far from unusual issue, and again can be done by this acting thing.
Agree that Bronte did not think of Heathcliffe as black, it would have been much more significant in the book had it been so. There is perhaps a hint of possibly having some foreign blood but it's more about his general otherness than anything detailed.
As noted, I think there is a difficulty with colour blind casting such as in David Copperfield with Dev Patel, and this sort of 'authentic casting' where, for example, Russell Davies will only cast gay actors as gay characters.
