The reason why the Saints didn't go for either one was because they were trying to make a run and getting help along the offensive and defensive line was a top priority along with other needs.
Lamar Jackson was drafted in 2018 that the year the Saints was the top seed in the playoffs and went to the NFC Championship game in the Dome against the Rams. By the Saints defense putting all of their eggs in the playoff basket paid off. In 2020, Jalen Hurts was drafted and the Saints was 12-4 and had a loaded roster and went to the 2nd round in the playoffs.
Yes, you can make an complaint that the Saints should have drafted a QB in the first round but the team was in contention for another championship run between 2017 to 2020. So taking a chance on drafting a rookie QB with a high pick during that time was taking resources that could be better used in other areas considering how important that time was.