Not in 225k miles, other than changing pads, discs, fluid a couple of times, and one broken parking brake cable.
Low as in the pedal is at the bottom of its travel and only applying slight pressure to brakes, or low as in the point where you can't press it any more is near the end of its travel?
What happens if you step on the brakes as hard as you can, does the vehicle stop quickly?
Try test driving another 4runner and see if there is a difference. If so, take yours into the service department and have them check it out, point out the difference.
4runner has terrible brake "feel" but the brakes functionally work extremely well for a vehicle of the weight. The brake assist feature will remind you of that occasionally when you aren't really expecting, or wanting it to.