KK, I think you're needlessly frustrating yourself. Ask yourself a fundemental question: Are you oriented towards producing good-tasting food for your family; or towards taking pictures of it?
While not mutually exclusive they do reflect differences that can effect the final result.
Take the Giouvarlakia. I wouldn't presume to tell you how to improve the taste. But to take a great picture would require some changes.
Right off, let me say that your camera angle is perfect. Could be slightly lower, but that's not a major issue. So let's look at the composition.
First, look outside the bowl (just as an aside, I love the bowl. Interesting in its own right, but it doesn't impose itself in a way that detracts from the food).There's part of the label of a beer bottle. No other "props." But anytime you show a whole-plate there should be other elements to help provide interest. Even a place setting would help. Or, perhaps more germane, Pour the beer into a pilsner glass and have it show in the photo.
What I'm saying here is that filling the frame with a plate of food is almost always disappointing. You have to either open up the scene, or close it down.
However, close is almost always better than far. Come in tighter on the bowl, showing only part of it, with at least one of the meatballs only partially on screen. For instance, you might just shoot the top two thirds of the bowl, from a lower camera angle, with some appropriate props included.
I would also get some additional color. Something that doesn't detract from the dish, but which adds visual appeal. Perhaps a sprig of mint? Or finely chopped parsley sprinkled on each meatball. Or...... but now we come close to changing the recipe to suit the camera.
Next, the reason stylists use those tricks and techniques is because the camera does not see the same way as the human eye. So, meatballs that were appetising when you ate them look pale and incipid when the camera looks at them. Which merely means you would have to do something to darken them up---and that might mean changing the nature of the dish.
The greens & puree shot suffers from the same outside the plate problem. But it has some of its own.
The main problem is lighting. That's why the greens look so dark. The other problem, from a photographic point of view, is that the plate is out of balance. There is far too much puree compared to the amount of greens. Again, this may not matter to the eater. But it does to the camera.
The way the lemon is sliced is visually boring. I'd have either gone with a couple of wedges, or cut the large piece with a serrated edge. Something, on other words, to provide a textural break.
BTW, contributing to your dissatisfaction is the fact the photo is out of focus. This makes the puree look like a pile of paste. If the onions were perfectly in focus, the whole thing would pop.
Personally, I would have plated that differently. The puree would be alone on the plate with the greens in a separate bowl. If possible I'd go with a boat-shaped bowl, rather than round or square. And, again, I'd have composed it so that most (but not all) of the main plate, and only a part of the secondary plate, were in the frame. I would probably lay down a curved row of sliced red onions, with the puree mostly covering them, for additional color contrast.
Now we talk about a major change. To enjoy the dish, you drizzle evoo over and around it, as you did. But, as you discovered, the camera isn't happy with that. Instead, this is when the spray oil comes out. That would apply just enough oil to provide some sheen, but avoid the puddling effect.
Please understand that I am not criticizing what you did. What I'm trying to do is show you why food photography and good eats aren't always the same, and if you want good food photos you may have to resort to some of those tricks and techniques.
Incidentally, I don't know how it works with digital cameras. But with regular cameras your choice of lens can have a major effect on the final frame. F'rinstance, I often use a 200 mm lens for table-top pix, because of the way it "sees" partial plates and the like. Until you've actually tried it you can't appreciate the difference in a final shot between using a long lens, from a distance, vs. moving closer with a short lens.