“If” being the operative word.
It would be difficult to read the final act of SR
as the clichéd “happy ending” - wherein Superman, Lois and Jason are (re)constituted as a nuclear family.
My own interpretation is that Richard is still in the picture, that he and Lois will remain together and that they will raise Jason. Superman’s personal fulfillment (his
“happy ending”) derives from a different source - the knowledge that he has a son.
The other interpretation is that Richard has nobly stepped aside. But this would only mean that Lois raises Jason as a single mother. In no real way does Superman represent (nor can he) Richard’s replacement as a full-time “husband” or “father.”
And even if you infer a Lois-Richard breakup, it would be a big leap to blame it on the active/selfish machinations of Superman. Clearly, both he and Lois were tempted. But by the halfway point in the narrative (and it is, literally
, at the halfway point), this temptation is essentially resolved. Indeed, in the yacht rescue scene, there’s a bit a conspicuous imagery/symbolism of Superman saving/preserving (not destroying
) the Richard-Lois-Jason family unit. And subsequently, Supes selflessly consigns himself to martyrdom - another altruistic act of preserving this family.