Congressional lawmaking is for the big-picture, long-term stuff. Agencies are supposed to have the ability to set rules as needed and respond quickly. This is a feature, not a bug.
And if Congress starts to see a pattern of a particular agency going way too far in some direction, then it can pass a law to further clarify the scope/limits of that agency whenever it wants. Congress hasn't given up any of its power. If it's not doing that, it's because it doesn't want to.
Experts aren't unbiased either. It is nice when the experts you like are in power but what happens when someone else comes in?
Experts may disagree, but it's still a whole lot better than non-experts disagreeing.
You'd rather this be decided by a failed football coach?
[0]: https://www.politico.com/live-updates/2023/11/14/congress/mc...