I would say it is 95% thanks to the incredible work of the modders, like you can see on Aris's AA halftrack (just absurd detail really) or Lucky Strikes' borderline photorealistic foliage - my ReShade settings just give it that extra pop.
Mainly some sharpening bring out the detail in the textures, bit of extra AA to smooth out the picture, tweaking the tones and most importantly in my opinion the colours, and then finishing things off with some grain/depth of field when taking screenshots.
The only problem is it gets so addictive flying around looking for little vignettes or cool details its slower than ever to play!