I think I read a different book than you.
I thought the book was fairly straightforward in its depiction of the relationship’s toxicity. Healthy relationships don’t include making out while defecating on the toilet.
The book depicts the relationship of a charming but manipulative and toxic narcissistic adult and a precocious youth eager but not quite ready for adulthood. CMBYN was originally intended to be written with Oliver as a woman. However, I suspect similarities between that plot and existing fiction, namely Bernard Schlink’s The Reader (adapted into the Kate Winslet Oscar winner) encouraged the author (who identifies as straight) to switch the gender.
The fundamental theme of CMBYN is evident in the title. Elio views “calling me by your name” as a transfiguration of souls or some such borderline personality bullshit. Oliver, a toxic narcissist, merely likes to call out his own name during sex.