This paper found about 60% energy recovery from regenerative braking in a BMW electric vehicle:
https://www.mdpi.com/2624-8921/5/2/22
That's a very significant heat reduction. Now in extreme braking conditions (ie, you're going really fast and you need to stop as fast as possible), that efficiency is going to drop WAY down because regenerative braking has a limit to how much power it can absorb. So you still have to design the brake system to handle close to the full heat load at least short term. But for long-term wear and tear from heat, regenerative braking is likely to make a big difference.
As a bit of trivia, for airliners, the worst-case scenario for brake heat load is a last-minute aborted takeoff, because you're at maximum ground speed, maximum weight load, and least amount of runway. The brakes need to be able to stop the plane, but they actually don't need to survive the event. And for a large plane like the A380, they don't. It generates enough heat that not only are the brake ruined in the process, the tires actually catch fire. But that's OK, because the plane is designed to survive the event while keeping passengers safe, and that should happen rarely enough that having to replace the tires and brakes in the event is an acceptable outcome. That's not really the case for cars, though. We expect to be able to come to a screeching halt from high speed and not have to do any repair work as a result.