Better for older preteens and family
I can understand the arguments that 15 may be a bit much. However this show is obviously not aimed at young teen audiences. Real world or not, a show that centers around underage drugs, drinking, and sex, isn't something that parents should just be "okay" with. Parents can't always control what the media puts out, but they have a right to feel whether or not they allow their kid to watch it. That 70s show may have teen humor, but it's more so for adults. I would recommend it's okay for preteens to watch with the family. The characters are very horny, sometimes an entire episode will center around sex. There's an episode where they go see a porno flick and Eric attempts to try out what he sees in the movie on Donna. The characters are also looking for ways to score or steal alcohol from their parents.
What other families should know
Too much violence
Too much sex
Too much swearing
Too much drinking/drugs/smoking