I am canceling a requisition and I want approvers to be added to the approval flow like any other change requisition. How to achieve this?

Ensure the Filter Rules of Requisition Approval Process has a rule set up with action Auto-Approve if Quantity or Amount has not increased and Field Path as DeletedLineItems. Configuring this rule will not skip approval nodes for a cancel requisition.

Core Procurement > Core Administration > Approval Flows