While BvS already tackled this concept, I still think a Superman film should focus itself on the immigrant story. I would just simplify the approach.
Standard three act structure rather than the five act structure revenge tragedy structure, and drop the religious allegory.
Keep Lex as the main ideological villain/alt-right proxy and use an actual rogue rather than Batman as the physical villain/incel proxy. That perceived impotency in relation to Superman is crucial to the social commentary.
Exclude the WW and bullet subplots and use that time to focus on Lois and Clark's joint investigation.
Keep the mounting disdain for Supes, but have Supes rejecting the narrative via more visualized moments of heroism. Allow him to talk about himself rather than relying on others to talk about him.
Last and maybe more controversial thing. If Cavill doesn't return, recast him with a POC. I'd personally look for someone of mixed race. Henry Golding type or someone who can pass for white. Hammer home the idea of this being a guy from two worlds and of his need to keep part of his identity under wraps in order to lead a normal life in America. Think of the many latinx/Asian performers who change their names to be more accessible.
Just a few ideas. As everyone knows, I'm a fan of BvS and I think its overall concept can be remade in a more crowd pleasing and easily digestible way.
I respect your views, but i feel If handled incorrectly, that sounds like a Capt. Marvel level cringefest and could drop like a bomb.
You can see where this can go wrong...
We're seeing issues with immigration, let's show America its favourite boy scout is an immigrant too.
Let's have the alt right as the enemy because... MAGA.
Let's change his skin colour too because... straight white male isn't in vogue.
I do think lois and clark should be an excellent source of social commentary on issues effecting the states and world right now, but it has to be balanced with a middle ground - politics is a spectrum.
I do think Superman can be used politically, but like you said... tread so carefully.. audiences escape the real world for a reason with movies - i would use the angle of him addressing how the states took him in, the states looked after him and he now calls them home - the possitive effects of immigration.
Trouble is, illegal immigration is just that... illegal. Each nation has a duty of care and no matter how it's said, it is not wrong to want to protect the boarder, make sure a process is used and respected but also to do what it can with said neighbouring nation so that they can create an environment where people don't want to risk their lives fleeing. Ofcourse, an election campaign saying how a big fat wall is going up to stop all the rapists etc is not the way to go.
Alt right... too topical.. and lazy - didn't they want to do that with Thomas Wayne and Baldwin but he stepped aside?
Superman being a person of colour? Totally changes up the dynamics - no need to explain why as it has been done, well, many times. But where i would say BvS screwed up is superman dying to doomsday didn't open up a world of John Henry Irons, cloned Superboy, eradicator etc which then opens the door to way more diversity using the S, imagine the Eradicator superman being this asexual being - someone like a younger david bowie, so other worldy and cool and a nod, not a slap, to the lgbtq community. Anyways, keep these ideas flowing, they're interesting.