One of the things that has hurt the Soul sales is Kia pushing up the price point. When I bought both of mine in 2012, the only cheaper car on the market was the Nissan Versa and the Chevy Aveo, and both of those cars drove and looked like junk, with felt carpeting, rock hard seats, pathetic 3 cylinder engines, etc. The Soul easily competed with the Honda Fit and Toyota Yaris, drove better with better options and was several thousand less. Now the Soul barebones with destination is about 22500, and that puts it a lot closer to a lot of other vehicles that are just nicer vehicles.
There is always going to be a market for a reliable, reasonably comfortable car that's cheaper than anything else out there. I think Kia is making a mistake ceding that ground. They want to be Toyota but there's already a Toyota.