As of this post update on 11/28 the plan is that the 18,000 Quixel legacy assets are now available to grab in bulk on the Quixel homepage until 2025 and it’s been announced that Quixel and Quixel Bridge will remain active until FAB is at feature parity.
The “Add All to Library” feature wasn’t added now it seems but this should bridge the gap until it’s prepared.