The op is not wrong but he is not entirely right. So is Askorti, not wrong but not right. The basic problem comes down to a couple of factors:
1. In the summer, there is never rain. In the autumn, there is never fog. No storms exist either. It is never cloudy except in winter. So for the 3 out of 4 seasons there is constant sunshine. It also bothers me, but Ill be patient until they add weather. We had several threads pointing this out already, none of them answered by the devs.
2. The banners are tacky. The colours are indeed too bright for anything that could be considered realistic or even just pleasant to the eye. I mean having 1 sigil and 2 colours is an abomination, but coupled with uniformed Age of Empires-looking soldiers it just hits extra wrong. As you could notice, soldiers in Custom Battle use an older system of banner generation, which has a tertiary color slot, more sigils, shield divisions etc. It is more pleasant and toned down than the company logos we have now.
3. Every item is coloured in the same colour as the banner. So imagine you have a red banner. Wear a scarf? Red. Tunic? Also red. Your soldiers? All red. Shield? Red. It is just ugly