The pale part is a separate problem from the watery part, and it has a separate fix: brown things first.
A slow cooker cannot brown anything. It never gets hot enough at the surface, and everything is sitting in moisture, so no browning reaction happens at all. Every recipe written for a pan starts by browning meat and softening onions, and that step is producing a large share of the colour and the savoury depth. Skip it and you get exactly what you describe — pale, and tasting like the parts.
So: brown the meat properly in a pan, cook the onions until they actually take some colour, and deglaze the pan with a bit of your liquid so nothing is left behind. Then everything goes in the cooker.
It is ten minutes and a second pan to wash, and it is the difference between the two versions.
Two related things worth doing while the pan is hot:
Bloom the spices and cook the tomato paste. Both change character with heat and both stay raw-tasting in a slow cooker. Thirty seconds in the pan.
Reduce any wine or stock in the pan rather than pouring it in cold. This handles part of the liquid problem at the same time.
If you take one thing: the machine is very good at the long tender part and cannot do the two ends. Do the beginning in a pan and the end with the lid off.