Use platforms for what they do well
Record keeping, identity, messaging and storage are usually better bought than built. The discipline is to use those services through stable interfaces rather than spreading vendor-specific logic through every workflow.
Keep the model yours
Entity definitions, terminology and reconciliation rules should be documented independently of any product. When the model is owned by the organization, changing a platform becomes a migration rather than a rewrite of the business logic.
Price the exit before you sign
Estimating what it would take to move away from a platform, at the time of adoption, is a cheap exercise that prevents an expensive surprise. It also clarifies which parts of the estate deserve an abstraction and which do not.