Welcome to the site! No, it's not a piece of junk. You just need to find a mechanic who can diagnose your problem. If everything is installed correctly and properly adjusted, your vehicle will track straight and the tires will last as long as they should.
While the OEM tires from the factory wear out quickly (35,000 miles) I doubt few owners still have their originals on their Patriot. A quality tire installed on a properly aligned vehicle will last 50,000+ miles at a minimum, allowing exception for aggressive off-road tires, but those are a different animal altogether; I'm talking highway tires under typical conditions. Don't be discouraged; find another mechanic. A franchised CDJR dealer ought to know more than the local guy because they get factory training, but that is not always the case, especially when it comes to mechanical repairs -- sometimes the local guys can do better. They've got horse sense the young guys haven't had the opportunity to develop.
One thing you said that intrigues me: your Patriot is eating up the brakes, too? This is unusual, frankly, strange. The brakes on both my Patriots passed 100,000 miles on the original pads & rotors (and rear drums), though granted it was my rears that needed replacing first. I'm not a mechanic, but those brakes failing prematurely may be a clue to whatever your larger problem is. Maybe someone else will see that and chime in.
Again, welcome!