[2020] Why is it 2.0? What is the big change here?

If a whole new engine and total rework of almost all graphical effects is "nothing special here" I don't think you quite understand the scale, resources and work that's required for such a development. It's not a minor thing at all. It's the sort of thing that happens once every generation of game consoles / standards. On top of that, we have major developments in the Naval area as well as the implementation of a whole new VTOL class and their respective mechanics. Huge interface, hanger and quality of life improvements and a plethora of other things.

These are massive developments to the game and the whole content of this patch is basically 2 majors worth. It's hardly a small set of changes.

All of this changes a significant amount of the game and thus is why the developers moved to a new 2.X version number from the 1.X chain.

Quite a lot has changed for a lot of ground battles maps. Similarly there are changes that will be noticeable in all modes.