That's blameworthy. Congress routinely cedes what are essentially legislative powers to such agencies. It helps them dodge responsibility. IMHO it improperly transfers Article I powers to the Article II branch.
There are 2 possible reasons I see.
1) having to change the political leadership of it every 2 years (instead of 4) means it possibly wont be as effective.
2) as there is both a "lawmaking" and "enforcement" aspect to it, it makes sense for it to be under "one roof" so to speak, and it would probably be more problematic for the executive to cede that to congress than vice versa.
perhaps there are other reasons? and one can counter the above reasons?
You can take a look here: https://en.wikipedia.org/wiki/Party_divisions_of_United_Stat.... You'll notice that the individual chambers of congress change hands less often than the presidency.
Additionally, Congress has a high incumbency rate. Even in huge swing years like 2018, the makeup of Congress remains largely the same.