> Currently those laws (which are technically called “rules”) are interpreted by the agencies themselves, with the reasoning being that the subject matter expertise of those agencies is most important factor in deciding any rule. The laws and judicial process works differently when it comes to agencies under the executive branch.

This was never true: it was simply the case that (under the principle of Chevron deference) that in cases of ambiguity, courts would defer to the agencies themselves. The courts still reserved the right to interpret the law, since that is literally their job.

Moreover, it's even less true since last year with the Loper Bright case, which overturned Chevron deference, and courts no longer defer to the agencies.

> Having an external governing individual is better than self-governance in most systems.

I don't know what this means. Who is an "external governing individual"? If you mean the president, I would say that he is (a) not external to the executive branch, (b) not entitled to decide matters of law by the Constitution, and (c) not qualified to decide matters of law by education and training.