Think for example how you would robustly check that resources of certain types are labeled in a way conforming to a given schema, or that would rewrite the label values in your stacks to a newer format. Linting CDK code can't get you this.
It's possible of course that I don't know enough about CDK and these examples have CDK solutions.
Imperative and declarative are not hard requirements for this but they make the domain easier to reason about and they are a good fit to the CF model of configuration-as-data instead (vs CDK's configuration-as-imperative-code).
Cdk linters can 100% do this. They can operate at the various construct levels including level 1 eg generated cloud formation. At this point it's just making a linter/visitor that says "if type is taggable then it must have this tag" and bob's your uncle. The l1 stuff is generated from the cfn schema and so will have tags correctly.
It's possible of course that I don't know enough about CDK and these examples have CDK solutions.
Imperative and declarative are not hard requirements for this but they make the domain easier to reason about and they are a good fit to the CF model of configuration-as-data instead (vs CDK's configuration-as-imperative-code).