In this case experts in their respective fields, at least that's the theory that was the justification for Chevron in the first place and it definitely held up

In this case experts in their respective fields, at least that's the theory that was the justification for Chevron in the first place and it definitely held up just fine. As in, the doctors the FDA employs would be the ones primarily driving decisions like "is this a drug? is it safe?" rather than the politically appointed judges who are categorically never experts in these questions as they have no education on the matter and are not expected to have education on the matter. Whether or not you believe them or agree with them is largely irrelevant. There is the political issue that the heads of these agencies tend to change political hands every 4-8 years, but moving all decision making to appointed judges is certainly not a step towards addressing that problem in the slightest.