Trade Desk, LiveRamp, others are developing increasingly privacy-centric addressability solutions and will continue to do so. Rearc doesn't aim to inhibit that, it aims to ensure baseline consistency, interoperability, and accountability.
Industry standards will always move slower than proprietary innovation, given the consensus/cooperation that has to be achieved across companies that compete. And if you think this pre-empts Rearc, you don't understand Rearc.