Hi Leo Dominick
Manually Identify inactive teams (those not actively using boards or managing work items).and deleting those teams safely.
If you're working with 600+ teams, consider scripting this via the Azure DevOps REST API or CLI.
Go to Project Settings -> Teams, select the team, then choose Delete. This removes dashboards, boards, and configurations but work items remain intact - https://learn.microsoft.com/en-us/azure/devops/organizations/settings/rename-remove-team?view=azure-devops&tabs=preview-page
Additional References:
Hope this helps!
Please Let me know if you have any queries.