Earlier quoted context omitted.
Probably. from the video: "This car performs better than anything we've ever tested before. Let me repeat that: not just the best electric car, but the best car. It does just about everything really really well."
They specifically state that their love of the vehicle is because it's an electric car -- that side effects of being an electric car yield a result that they enjoy (e.g. low battery packs helping weight distribution, etc). Does that really make every other car "mediocre"?
In general, I got the feeling that "mediocre" was referring to all the shitty interfaces on cars, and general lack of polish that Tesla seems to be doing correctly. This is something that car companies could / should be doing for minimal effort since they employ so many and spend so much money, but they're not.