The most noticeable thing for me, is that, it looks like an airbrushed basecoat. Soft colour, large surfaces covered by the same minimal tones, and minimal transitions.
To be as honest and helpful as I can, the GW kit is doing a lot of the work for you, as FW kits often do for others. To bring your skills up a notch, you will have to spend more time managing light, transitions of colour/light, and using your techniques to do the work instead of the kits.
I think the concept of basework as an afterthought is a big point, as Ive found that most gamers who become painters paint models, while top painters, build characters, scenes, personalities, ideas and so on. Creating a vision will help you better present, organize and deliver a certain mood or idea with your colours, composition and basework,
Hope this is helpful for you!
You have by no means done bad work, but the best part is, you can do many things to improve! (itd be boring to be perfect

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