Kicad is where you want to go in the free price category of ecad programs.
Once they improve their library management system, it will surpass Altium in nearly every way possible.
But yeah saying it is as advanced as Altium is a stretch.
"Good enough for all but the most advanced high-speed stuff" is probably better description.
Also — the common open source refrain “there’s a scripting interface” is just another way of saying “the feature isn’t implemented, but you can implement it yourself.” It’s not terribly helpful.