Superman leaving Earth thinking with HOPE that his world might still exist is not so far fetched and besides as I already stated that was part of a plot by Luthor to lure Superman away from the planet and it worked.
Again, however, Singer's own conceit (that this was a direct sequel to S2 [and, therefore. S1]) contradicts that.
Superman knew that Krypton was destroyed. Jor-el showed him the destruction through the crystals. Jor-el also explained to him that Zod, et al, were from the Phantom Zone.
So, Luthor would have had to use a pretty damn good trick (though, of course, we weren't actually show what the trick was)(but that's a different problem).
As for Lois...I wouldn't go far as to lump her into a mature relationship with a good man so fast!!! Sure this must've been an attempt to move on from Superman who for his own personal reasons chose not to tell her why he was leaving but we all know that Lois was also rebounding and this is one of the reasons why she never fully committed to Richard
Even if that was the case (I admit my memory of this part of the movie is vague at this point) none of that would be known Superman except for the fact he was stalking her. So, that's just more evidence of his being creepy [or at least not the Superman we expect] in the film.
...oh yeah and let's not forget that SHE LIED to Richard that he was the father of her child.
Again, I don't remember her telling Richard the kid was his. I thought he knew she was a single mom and started dating her.
But I'll take your word for it that Richard thought the kid was his.
Two things about that, then.
First, it tends to indicate that she and Richard had been together for a long time. Again, that's a reason for Superman to back off, not a reason for him to start spying on her.
Second, getting back to Singer's whole "sequel to S2" setup, you can't hold that against Lois because, as noted above, Superman wiped her mind of their whole love affair. Which (again, as noted above) he did out of sense of duty to earth...the same earth he then turned around and abandoned.
Look, you asked why people had a particular view of the movie. When people give you the explanation you asked for, even if you disagree with their opinion, it's silly to get dismissive and demand they change their mind.
Why did you ask if you didn't want to discuss the issue?