Mitsubishi has huge potential in the 4WD market, and they are pretty big in that segment in places like Australia and the Middle East. Unfortunately, this is not a big segment in the North American market. To clarify, for the average American customer, 4WD is something they like to have as "backup" in bad whether conditions and technology is so much relied upon to cover a lack of skill. Elsewhere, people actually take these vehicles off the road to some extreme conditions. Yes, the Jeep Wrangler is a popular vehicle in the U.S. for the likes of mudding and rock crawling, but that's not the segment the Japanese are targeting for their 4WDs, and this particular segment isn't as big as other markets. Anyone who says otherwise can tell me how many Land Cruisers Toyota sells in the U.S., compared to the likes of something like the Sequoia or 4Runner. Nissan also isn't selling their Patrol in North America either.
Vehicles like the Land Cruiser, Patrol and Pajero are geared more towards off road use and, although a lot more luxurious than previous generations with better on road manners, they're not really the first choice for everyday driving compared to something like a Sequoia or a Suburban. They have some of the best heavy duty suspension offerings around, but they ride harsh, their turning radius is wide and they were not engineered to be highway cruisers. Soccer moms look elsewhere. That right there explains why the Montero/Pajero was pulled out of the USDM, which was their strongest attribute.
Mitsubishi is capable of producing decent cars, but like many other manufacturers, they are not perfect. People quite often point out those oil burning Mitsubishis, but forget other manufacturers, particularly domestic, shoot themselves in the foot with cost cutting. Ford's two thread spark plug holes and nylon timing chain tensioners on the 4.6L, IMO, were a lot worse than bad valve stem seals on a 6G72.
That being said, their vehicles lack market appeal in North America for one reason or another. Their products are not exactly [censored] either - the brakes on the Lancer are a lot better than the Corolla IMO. I don't know if it's because of things like "refinement", marketing or simply costlier spare parts. Hyundai is pushing hard, but it seems there's a lot of brand loyalty that's hindering their efforts. Before going to CA, I have never in my life seen so many Toyotas and Hondas. When the rental company didn't have the Suburban I wanted, I wanted what they referred to as a "full-size" (mid size) and asked for an Impala over a Camry/Accord. The manager "couldn't understand why anyone would want an Impala".