I love ACC in my 2020 accord (which is the same generation as your 2019). I've never had it hit the brakes hard enough to be jolting, even when a car changes into my lane.

The LKAS is hit and miss, like you said, unless the lines are very clearly visible, it can't stay in the lane. I wish it looked at the car ahead to help with lanekeeping. But it's never surprising when it loses sight of the lane markers (though it does tend to drift to the right at exits, but it doesn't make a sharp move). But even in its current state, LKAS is great for long freeway drives.

Surprised to hear that. The ACC on my 2019 CR-V is the best adaptive cruise control I've used, a lot smoother than ACC I've tried in substantially more expensive cars. I agree the LKAS is pretty crappy (off of highways, it seems closer to 60% of lanes), but I've never experienced anything with it that's caused actual problems. The crappiness just comes from it frequently not knowing where the lane is, but I leave it on at all times for the times where it does recognize them.

I've never tried other ACC so it might just be me.

The specific situation is this: I live in Los Angeles and set ACC for max following distance on the freeway. Inevitably this means that someone will use that space to cut across 3 lanes and, as soon as do, ACC will rapidly slow me down to put distance between me and the new lead car. I'll find myself suddenly under 50 on the freeway as a result. maybe that's just how ACC is but imo the PID controller or whatever could be toned down a bit.