The flashback being from Booth's perspective should indicate that his view of Lee doesn't necessarily reflect reality.
That's not all Superman is about. those who push that belief generally want him out of the way so other heroes can get the spotlight, to put him on a pedestal so we don't have to engage with him and so he can inspire others to be better than him. A lot of Superman fans are sick to death of his passive inspiration and humility getting too much focus. Sorry, but screw that noise. They don't have to be happy with anyone equaling him or surpassing him in specific ways that he started. Why is that necessary to begin with?
The show is not subtle about its messages. One of its episodes is called "Nevertheless, she Persisted" which tells us all we need to know. Clark not caring that Kara beat him under those circumstances is not OOC at all, nor should he be the hero in her show. But the only reason that scenario is cooked up and those words placed in his mouth is because the writers want to prop up Kara in comparison to him. And considering the timing the episode came out, of course Superman fans are annoyed with it. Some reactions are overblown, but the basic criticism isn't invalid. If the only times Superman's power is respected is when he goes evil in video games, becomes a zombie so he can slaughter Wonder Woman, or briefly go out of control in JL (where everyone was talking more about Cavill's CG lips), what exactly is there to get excited about? Nobody was asking for any of those.