ACC generally has a 3-4 second time interval that it permits between you and the car in front of you. I live in SoCal, so a lot of my driving is on very aggressive routes. The 4-second gap is mechanically safe but it's practically unusable because it creates a void large enough to invite other cars to lane change in front of me. So when that car merges in, the ACC detects a violation of the safe braking distance and decelerates to reestablish the gap. I call it the "cut me off" loop when we're on trips.

And before anyone suggests that I start tinkering around with the settings, I have adjusted it and the damned thing just resets itself constantly.

Ah yes, I never used that. My car isn't very recent (about 10 years old now), and I drive very little (about 2-3k per year; I take the train to go anywhere far) because I hate it. But the adaptive part would make it much more useful indeed.

However, something that is extremely annoying in France is that speed limits tend to change very often and abruptly. I just think that trying to solve the problem solely at the car level is always going to have too many limitations...