Best thing people can do is wait. If performance or driving feel is not what you expected, put these sims on hold until they're released or very close to release. Expecting optimizations, faultless graphics and physics when AC, rF2 and pCARS are still far away from release date is an expectation without much sense.
Also the thing that is really killing rF2 is their choice to focus on physics first. Tim himself admitted that if they had to start again then maybe they would focus on getting the visuals polished to a decent state first before releasing anything to the public.
For someone like me i prefer the ISI way of thinking tbh and respect the way the focus is on the important parts of a racing simulation.
SMS: starting point was something they already had, which was gfx and sounds. Then building up on existing tire physics, correcting what was wrong and ending up implementing entirely new features.
ISI: physics has always been the pivot point in their racing sim developments. Fortunately so. Then launch waves of strong developments in the graphics and sound engines, always with an eye to netcode. Good approach.
Kunos: same as ISI, though they seem to be more advanced in terms of eye-candy stuff.
Maybe SMS initially targeted a wider audience, but they emphatically state the hardcore simracing group will also be satisfied with the end result.
ISI and Kunos seem to eye (initially) different audiences. Dev wise, similar, I'd say, but whereas ISI knows they have a core audience which, in the mid to long run will attract other types of simracers, Kunos is targeting casuals as well - Marco M. is quite clear on that.
We'll see how it plays out.