The entire point of Smallville is he wasn't Superman, he was Clark Kent, with underdeveloped or entirely missing powers, bullets bruise him in the early seasons, he didn't discover heat vision until he got hot under the collar, he couldn't even fly and so on.
But even then, most of his 'losses' come from facing a new enemy with abilities he never encountered before, but he then adapts to the new gimmick enemy of the week and kicks their ass, like most shows of its type.
Supergirl is not Smallville. She is Supergirl, right out the gate, fully powered. Yet she gets her ass handed to her in a fair fight with no gimmick and has to be rescued by the flipping military? And of course this is after said military takes her down, captures her and depowers her with no effort at all. She only beats the bad guy because he decided to become an idiot at the right moment.
It's just a crap way to introduce a character, she isn't just getting her powers and learning them, she isn't an intentionally gimped version of the character, it's "Here's you brand new Superhero...who's really weak despite having ridiculously strong powers"