There's this thing which has subtly bothered me for years in regards to how the DC fandom disregards and downplays Clark's relationship with his own supporting cast, in a way that doesn't seem to happen to other DC characters in quite the same way. And as I've read more comics from different eras, I've seen the patterns in canon which have led to it.
The only exceptions to this are Lois and the Kents. I understand why Lois escapes it, she is inherently the most important supporting character (though people are starting to notice the same sort of sidelining happening to her as the trend worsens). But the Kents having this much importance only makes sense with the type of stories we saw in post-crisis and afterwards. Basically, people believe they're the only important supporting characters because DC spent decades undermining every other non-superhero relationship or dynamic Clark had. It's hard to explain if you haven't read comics from the post-crisis era, and contrasted them with ones from the silver age and bronze age. You notice reading older Superman comics that there was more variety and unique continuity in Clark's relationships.
To a degree this happened because of the pared-down approach to the mythos in post-crisis (i.e. no Clark!Superboy so Pete and Lana have less relevance, no unique settings within the mythos and less reason to visit their associated characters, no backstory with Lex). The writers struggled to use them in compelling ways because that history was torn out, and there was a subsequent need to introduce new characters to fill their old roles. As stated before, the only real exceptions to this were Lois and the Kents, whose roles shifted to match the new canon while maintaining significant dynamics with Clark himself. And now many people will question or resist the other characters being given more important or complex roles like they used to have.
There are specific stories which led to this perception and newer ones which validate it because it's simply the status quo those writers were brought up on. And I think the fact that these patterns have borne out in canon for so long both explains the fanon trend and reinforces it. People aren't pulling stuff out of the air, it's a result of how DC has marketed the character of Superman for a while. It's just become increasingly obvious in recent years.
It's interesting being in a fandom which still talks about the knock-on effects of a reboot from 15 years ago and the potential stories, continuity and character development we've lost because of it. It's the exact same way I feel about Superman. The reboot affected his individual characterisation and mythos so profoundly it's never recovered and probably never will. It just happened in 1986.
