If they believe congress shouldn’t have the authority to delegate authority so broad then the way fix isn’t to eliminate the delegation but to require that congress reviews the regulatory agencies to see if they’re acting as according to their intent (yes there’s risk of abuse for this too, like endless micromanaging, etc, this is just to defuse the constitutionality argument)
Just read a bunch of audit results and discuss relevant court cases involving the varies agencies in front of congress and let them rubberstamp it