the only people who say that Superman "shouldn't show emotion" are the Snyder cultists and those who never picked up or watched anything with Superman in it.
Unfortunately, we live in a time where politics and issues such as a crisis of gender/masculinity have consumed the discourse surrounding film, games and other media.
The campaign and first term of Donald Trump was shaped - literally - by GamerGate (look it up).
And in this insane radicalization of men - certain IPs and characters have been centered as paragons/symbols of ideal masculinity. And they're framed as being under attack, therefore, your masculinity is under attack too.
Superman is one of those characters. Snyder's version, one of stoicism, God-like strength, frustration and giga-chad jawline is seen as a form of peak masculinity. Snyder's films being dour, angsty, faux-deep slogs is also what they feel represents 'cinema'. Because seriousness = credibility. Which they desperately want.
They never 'got' Superman, though. Superman is as non-toxic of a masculine character as can be. He has emotions, he has doubt, he has fear and feels alienated. He is gentle at heart because he knows how strong he is.
He does the right thing. And none of this makes him boring! It makes him compelling, that someone with the strength and powers that he has
chooses to do the right thing and be a good person. That is an anomaly in our world, and it remains his greatest superpower, though.
The fans you're referring to are the types who don't understand that power is not brute force; but look at our current American politics. Brute force is now considered peak power.
Superman is aspirational. But their idea of what is aspirational about him asks nothing of them - it only asks for nihilism, brute-force and stoicism.
It is like that scene in
Schindler's List where Oskar describes what true power is. Restraint, humility, and forgiveness is true power. Not force and exercising your ability to exert will on others. That's why Superman is a great character and endures.
Goodness is not boring.
Brute force, stoicism and angst are not some form of masculine perfection.
One can dislike this film or how it looks quality-wise, but if you tell me that it's not 'Superman', then you don't understand the character.
I'm tired of a character as good as Superman being bent and contorted into something he is not.
Superman IS goodness.
Not toxicity.
