Unnecessarily hostile opening, but full separation of powers as written in the Constitution.
> Should the executive branch agency make decisions by fiat, without due process?
It should not be adjudicating any kind of legal controversy. That is not the role of the executive branch.
> The use of due process doesn't make them a judiciary; it's just a more fair way to make decisions within their purview.
It's very often worse. Executive agencies often have legislative functions, i.e. APA rulemaking, as well judicial functions, e.g. in this matter. The SEC is another one, (see SEC vs Jarkesy currently before SCOTUS).
> Should we move every such judgment out of the executive branch's hands?
Yes.
> But the heart of this issue is, as is well known: There aren't nearly enough capacity in the judicial branch to handle all that work. It's a trick to prevent lawful and needed regulation from happening by severely cutting their capacity.
Total BS.