Penny has evolved in plenty of positive ways (maturity-wise, confidence-wise, being-able-to-go-toe-to-toe-with-Sheldon-in dealing-with-his-fussiness-wise), even though the character relied on her physical looks and didn't spend a lot of time developing much else in the early seasons. The never-ending string of jokes about Leonard’s unworthiness of Penny is the series' worst ongoing cliché, especially 12 seasons in.
How's about we all just accept that Lenny are deserving each other and find humor in other areas of their coupledom?
"Comedy is about things not being right. Things are running beautifully and everyone’s behaving appropriate and intelligent is not funny." (J. Cleese)