Maybe because heroes are dynamic, and solve things through action?
Action takes many forms, would you deny Oracle is active? Or Professor Xavier in his original wheelchair?
Maybe because comics are a visual medium and a physical fighter is more fun to draw and look at?
But variety is the spice of life, if everyone is a kickass fighter, then there's no variety.
Maybe because fans were apt to question how she could be so poor in combat situations and yet remain alive and with the team,
Because her powers are effective and versatile in combat already. The fact she could use them whilst standing still is pretty much irrelevant unless slam bang action is all you crave.
when logically one of those would have to give --just like they did with Doug? If you recall, he was killed by popular demand.
One offhand comment from Louise Simonson to one side, I'd dispute that, I recall no bias against him in lettercolumns or in the local comic shops I frequented at the time (and much positive response to his mutation being so different), and no one liked his death that I recall.
And as I pointed out, the character was motivated by a desire to stop being helpless and become a warrior,
But I can see no evidence that she WAS "helpless". The battles she lost were targetted assaults by Slaymaster, Mojo/Spiral and Sabretooth, none of whom are lightweights in their fields.