Actually, the saudi family gives citzenships to tribes that have made pledge to the saluli family. Many did but big tribes did not like for example Al 3anyza they are I believe the largest tribe of Arabia.
Because they deny them and they were the bosses of these places until the White man funded Saudi family to fight them and they lost.
Some Arabs can't get the citzenship and they are classifed as bidouun which means without.
A way to get a citzenship is stay before 1950, many somalis done this like the 100 men that the sayiid sent. Now they are all saudi citizens in hundreds if not thousands living in Makkah, Madinah, Taif, Sail and Jeddah.
Another way to get in is to marry a Saudi citizen woman, I know you guys don't like Arabs but its the only way.
The final way is to get a prince and contact him and tell him for citizenship. This one is the most challening but the premium way of not staying a long term iqamaah holder.