Actually, it's not until age 21 before a USC can petition for a relative. The system has always been about family ties and family unity. Many EWIs are facing a 10 year ban, so it doesn't matter if their children can file for them or not. They would have to go to their home country for their consular appointment, and ultimately cannot return until 10 years later. He's helping those people via the EO, and rightly so.
If you want to make a sensible point, then say something along the lines of the following: "the system should change reflecting both family ties and meeting the needs of our changing economy. That way farm workers, relatives of LPRs/USCs, and the tech industry get a good deal as far as immigration goes."
And I think you seem to neglect the fact that many of the same farm workers you are concerned about have USC children. If I recall, 300,000 or so will be helped via the DAPA program.