That is absolutely not the reason. It's because slow cookers generally cook at a high temperature for far longer, resulting in far more muted flavours. People generally don't leave a stew to cook for that many hours when using the stovetop, since they pull it when it's ready. The weird "slow cooker flavour" is simply due to overcooking.
I don't have enameled cast iron dutch oven I actually only have an aluminium thick base saucepan and my old slow cooker was some kind of coated metal, like teflon
You probably know this already, but teflon (for the same reason it prevents sticking) essentially prevents good sears and good fond. The price one pays for ease of cleanup.
I wouldn't say it prevents good sears but of course it prevents good fonds. Anyway I don't have it anymore since my wife became a vegetarian and honestly I enjoy cooking directly too much. I don't want to leave it to cook when I can get better results on the stove
This. Teflon temperature limits you away from the crazy hard sears, but that's ok, the Maillard reaction hits its peak around 350F so you still can get plenty of great browning flavors.
I find the biggest difference is in nonstick, the fond sticks to the food instead of the pan. So you can't deglaze and make a sauce. On the other hand, sometimes the nonstick is better, like with seafood imo.
