Y'all always so uncomfortably weird when it comes to Tyler's Superman. (Though I understand preferring Routh's, as he's awesome, and fucking massive)
He's weaker than Supergirl, it is what it is.
I know Supergirl is often heavy-handed when it comes to stuff like that, but I feel it's disingenuous to apply it here. The way I see it, they got tired of people always asking where Superman was at, especially for the bigger threats. Given that Supergirl is the main character, not him, they eventually made it very clear she's stronger, as well as sending him off to another planet, all for the sake of justifying her being Earth's primary protector. Because again, it's her show, not his.
If they were all about making it some trite message of "Girls can be stronger than boys", then this show frankly would've done that from the beginning. Their approach has only ever been a reactionary response to the perpetual shadow that Superman cast over Kara and the show.
I always took it as Kara is just... Angrier than him for lack of a better word. Like when she laser beamed red tornado into dust she was channeling all that rage and pain she keeps bottled up all the time.
Clark just doesn't have that much to be mad about.