Not everything is a stateless HTTP microservice. Solutions like ECS start to fall apart when you try to run stateful workloads, especially when the lifecycle of the workloads needs to be coordinated to prevent loss of availability or data (i.e. cannot tolerate 2/3 of the containers being knocked offline at the same time). AWS does not offer a managed datastore (e.g. RDS) for every datastore, and many of the datastores it does offer (e.g. MSK) are "let's tick this box in the quest for covering all our customer needs" but not cost-effective for production workloads.

Maybe, as a product, you make a decision to tell your customers, when you need to run something like that, go hire DevOps and migrate off. But you'll be more credible if you're up-front with what kinds of workloads you don't intend to support, so that customers who have a strategic vision for engineering can say, hey these guys will be great for me for the next few years, now I'm more likely to buy in.