ACC may seem easy. But if you want to get competitive times it's just endless car adjusting and tyre pressure fine tuning. For example I can't go below 1:58 on Nurburgring GT track on ANY car. The best sim racers have insane lap times like 1:54 and 1:55. I just can't duplicate that. I haven't tried recently though... I just don't know how to set up the car properly.
If you want to compete against the best, ACC is FAR from being easy.
But I play AC 90%. Automobilista 2, rF2 and ACC occasionally. RBR too, which is still amazing. There is just something about AC driving, tyre grip, the FEEL of the car which is unmatched. And the mods... it's insane that I can play (almost) all 80's and 90's F1 seasons. Tracks are mostly excellent and it's so easy and convenient to fine tune the difficulty level. You can always make the ai faster by just opening car.ini, engine.ini, etc.
The feeling I get from driving those vintage F1 seasons is unmatched. And the 80's and 90's tracks are mostly masterpieces. The whole 88 track pack is pure genius.
For us classic F1 fans there's nothing like AC, it's the GOAT.