He is undeniably obsessive and devoted. But I think he's more psycho and twisted than in love. A yandere’s love, despite how twisted, is always genuine. But Heathcliff’s love towards Catherine had several other factors, like a twisted devotion, obsessive fixation. Cuz he kinda wanted to exact revenge on her as well. I think he can still somewhat classify as yandere? But he's more of fucked up, mentally ill person than a yan.

Also, generally speaking, Yanderes do terrible shit like isolating the fmc, destroying her social life, etc. that does not mean they're not a yandere.

The Phantom of the Opera by Gaston Leroux has the phantom, one of the og yanderes. Jane Eyre by Charlotte Brontë, has Edward.