The error message "We can't retrieve all the available events, it seems that they are too many different events. Please check your implementation" in the Personalization page indicates that the Personalization strategy could not retrieve all valid events because they are diluted by malformed (invalid) events.
As a result, the strategy is limited in the number of valid events it can retrieve.
To resolve this issue, you can navigate to your Event Debugger, review the invalid events and identify areas where your events implementation needs improvement.
You can follow this guide on debugging events.