Why are subtle flavors like almond or cinnamon lost in my cake? It only seems sweet and sugary.

Some cakes are mild. There is no avoiding it. Sometimes you can add more of a particular spice, but other times you might realize that the strong flavor might come better from the frosting or icing.

If there is a particular flavor you are trying to highlight, try almond extract in your frosting, or coconut flakes sprinkled on top. In coffee cake, there is often streusel (which has lots of cinnamon) on top. Yummy! Good luck with your baking!

No, do not decrease sugar. Sugar in baking affects texture, moisture, and leavening. You can reduce sugar, but understand that the end result might not be great or as intended.

How old are your flavorings (extracts, ground spices, etc)? Most ground spices have a shelf life of 1 year (2 if properly stored) before they lose their volatile oils (ie. flavor, scent). Extracts have a shelf life of 6-12 months. Vanilla extract is the exception to this rule. It gets better with age. So check your spices and extracts and see if they are still 'good'. It might be worthwhile to get new flavorings and make a cake. If your spices/extracts are relatively new, increase the amount. But don't mess with the sugar, or fat.

Did you add salt to your cake batter? As with savory items, salt enhances the flavors of sweets as well. About 1/2 teaspoon should be enough to bake a big difference.

If you add a link here to the recipe, we might better be able to suggest reasons the flavors are lost (dominated by other flavors?) and possible adjustments...