I think there are three problems with most slow cooker recipes.
1.) My hi/low setting probably doesn't match your hi/low setting. From the get go, we're cooking the same meal at two different temperatures.
2.) A lot of recipes seem to call for low setting for 8 hours. This works well for a lot of people with a standard American work day, since a stew/soup will stay above safe warming temperature in a nearly sealed pot. However, the cook times are too long. Thawed chicken for 8 hours on low almost never turns out with the right texture. In this case, it's convenience > taste.
3.) The flavor is cooked out of the ingredients, and/or there isn't enough seasoning or too many ingredients. When you get the seasoning right, too long of a cook time can dull the flavor. When there isn't enough seasoning, then your meal is bland from the start. When there are too many herbs and spices, you get a mish-mash of flavors that are all competing for attention. There was an article on here a long while ago that categorized foods into low and high amplitude flavors. Something sharply distinctive was high amplitude (think nacho cheese Doritos), while a low amplitude food had weak, hard to discern flavors (plain grits). Too many different ingredients can lead to low amplitude foods, and when I see an ingredient list with 15 different herbs and spices, I almost always steer clear.