You're looking in the wrong places. Mountain bike specific clothing is usually looser and more low key than road bike stuff. Yes there are jerseys with graphics but there are lots with plain solid colors too. As far as shorts go, why would you thing you have to wear lycra tights? There are plenty of baggy shorts with liners and you can buy just padded liners to put in regular old cargo shorts. Cycling clothing is usually more expensive than buying a shirt at WalMart, but it will last for years and years. I have cycling jerseys and jackets that are 20 years old and I ride a lot. Shorts don't last as long. You can find perfectly good active shirts (read not cotton) at Ross for $10. If I'm going to ride for an hour anything will do, if longer then mtb baggies and a good athletic shirt of some sort make the ride much more enjoyable.
And about those lycra tights, road cyclists don't wear them to show you their toned butts, try riding 30 or 50 or 75 miles and you'll painfully discover the advantage of the pad and shorts that don't chafe the skin. Having been riding bikes for 40 years none of the clothing bothers me and I've worn all of it at one time or another. These days I wear the tights under cargos and everyone is happy! Surely seeing people riding bikes in the fancy kit can't be as traumatizing as what you see every time you go in a WalMart....