Credos would be required to level a certain ability past a certain point. Adding a ceiling that could only be surpassed by completing the respective credos, this cap would vary depending on the ability and credo required, the easiest to obtain would have a much lower cap whereas the hardest credos to obtain would have a much higher cap for example:
To get past 50 survival and exploration, you'll have to complete the forager credo
To get past 300 smithing you'd be required to complete the blacksmith credo
Credos are required to collect certain localized resources or get certain exp events. Only the ones who are acomplished and proficient at a certain activity (people who have completed the credos) should be the only ones able to extract these valuable resources.
This might help with the several dozens of alt bot hearthfires next to the most important resources that we see everywhere.