You're confused about how the system works.

Notable locations, and your ability to use them, are based on research. When and what level of notables show up are are also based on the tech research of the other factions.

In order to get access to those notable locations, you have to research your adventuring/domination tech up.

The level of your sovereign and champions has nothing to do with the notable location level of your faction. A level 1 champion can go to a level 5 site if you've researched it.

Go to your Kingdom report tab, it will tell you what the notable location level of your faction is, versus the world.

The system is currently wonky in that, when other factions research adventuring tech, it causes way too many notable locations to appear around you.