IMO Pulumi and CDK are an opportunity to simplify your infra by capturing what you’re working with using higher-level abstractions and by allowing you to refactor and extract reusable pieces at any level. You can drive infra definitions easily from typed data structures, you can add conditionals using natural language syntax, and stop trying to program in a configuration language (Terraform HCL with surprises like non-short-circuited AND evaluation).

You still end up having IaaC. You can still have a declarative infrastructure.

That's how we use CDK. Our CDK (in general) creates CloudFormation which we then deploy. As far as the tooling which we have for IaC is concerned, it's indistinguishable from hand-written CloudFormation — but we're able to declare our intent at a higher level of abstraction.

Absolutely, the best case is it's much better, safer, readable etc. However, the worst case is also worse. From the perspective of someone who provides devops support to multiple teams, terraform is more "predictable".