You don't appreciate him because you're not old enough to have seen him. He was only healthy for a few seasons. Penny in his prime was not overrated.
I'm 35; I saw Penny's whole career going back to his Memphis days. Great player, but VERY overrated. People talk about him like he was Kobe/LeBron level. He wasn't; more like Brandon Roy/Joe Johnson level. In other words, he was a great player but not elite.