There will still be a degree of deference, it just won’t be absolute like Chevron requires. Agencies will still be presumed valid, but that assumption will become rebuttable.
Everyone likes to point at the EPA with respect to Chevron deference. We need to look at the FCC under Ajit Pai. Chevron deference should not have protected the FCC when they decided to suspend Net Neutrality in 2017.
We should also be able to challenge NHTSA’s CAFE standards, which are driving manufacturers to make larger cars because it’s harder to make small cars compliant than larger. But, because of Chevron deference, we can’t: the agency knows best.