There are very few things you can do in a slow cooker without compromises that affect the taste, mostly because of the limited temperature range (mostly they don't get hot enough) and the fact that most of the time you don't want all of your ingredients in for that long. This can be mitigated of course, but once you are pre-cooking some things and adding others later, you lose the primary appeal of them.

Most low-and-slow is better done in an oven, so the main thing you are left with is fire safety (e.g. if you want to leave it going and go to work). If you aren't careful you trade that off for food safety, anyway.

I see the appeal for convenience if the mediocre results don't put you off.