Coconut milk can mean several products on a shop shelf. A thin drink intended for cereal is not the same as a rich canned cooking milk, even when both have a coconut on the label.
For a recipe that depends on richness, check the specified product and its fat content. Light canned coconut milk gives a different result from a full-fat version. Sweetened cream of coconut is another ingredient again and can turn a savory dish unexpectedly sweet.
Separation in a can may be normal for the product; stir the contents together when you need an even mixture. Follow storage directions after opening. If you dislike coconut flavor, look for a recipe built around another creamy ingredient rather than assuming that garlic will hide it completely.