They're missing a feature called Target Wake time on the AX8,AX12 and AX20 and there are a lot of firmware update issues that people are having so they have to revert to their old firmware.
Also here's a link which has some issues mentioned on the netgear community forum but haven't been answered yet: https://community.netgear.com/t5/Nighthawk-Routers-with-WiFi-6-AX/Nighthawk-App-missing-Parental-Controls-and-Security/td-p/1831175
And there are plenty of complaints in the netgear subreddit.