>>36806365They're not incompatable.
Older 3DSs have an issue with WPS/WPA2 settings because they weren't really a thing or commonplace while it was being made. To fix it, all you have to do is lower your security to ONE of those, or most of the time just setting the 3DS up using a WPS button works too. To figure this out, you just have to not be a dumbass and look into it for more than 10 minutes.
Newer versions of the 3DS and obviously the N3DS work just fine on it.