If dessert makes you feel bad afterwards, someone did something wrong.
And it wasn't you.
Don't get me wrong, I do not make low-calorie desserts. But I push back when desserts are categorized as either decadent & rich or on the lighter side. I think we can have all the yums without the gut bomb often associated with American style desserts. The trick, as it were, is two-fold: layers and contrast.
You can definitely make a decadent yet less heavy cake, and I often do. But to capture the full yum experience you need multiple layers. This doesn't automatically mean a layer cake per se -- it could translate to a cake layer, a ganache or custard layer, a mouse layer, a finish layer, etc. And equally important are the differing textures between those layers. A light sponge cake with a thin layer of ganache will often have the impact and mouth feel of a richer cake, but with less heft and more distinction.
Add in a mousse layer on top for a lofty, creamy texture, maybe a thin crunch layer underneath, a decadent but very thin mirror glaze on top and the resulting experience takes on excitement and even a little discovery.
Remember that scene in Willy Wonka when Violet is chewing the magical gum that transforms from turkey to stuffing and all the sides, then blueberry pie? We experience those flavor distinctions in a layered cake as well, temporally. Oooo there's that delicate sponge cake but oh that rich chocolate pop, then ohmygawd the mousse! The experience becomes sequential in a way and we get to experience one thing, then the next, then the next.
With contrasting layers, we read the difference between them as richness so we don't actually need more fat and sugar for maximum enjoyment. We get all the satisfaction without feeling terrible afterwards.
I take the same approach with flavor contrast. Can we have a mellow vanilla layer right up against a bright lemon pop? How about a bittersweet chocolate next to a sweet creamy coffee next to a smoky hazelnut flavor? The imagination runs with those flavor combinations -- the key being the contrast within the combination.
The next time you're putting a cake together, keep in mind what goes with what, and in what order. I bet you'll find the leap to the next level of yum lies in the relationship between the layers every bit as much as the layers themselves.
Then your cake game will be unstoppable.