The challenge with serverless is building systems that rely on more complex backend processes and existing code and doing things like testing using most of an existing codebase. Serverless is great for nodejs/javascript stacks that are database and front-end heavy but don't need more complexity like queueing, event streaming, or more complex architectures. Then serverless becomes a huge mess normally and the developer experience becomes a giant catastrophe, as well.
Here the OP kind of got caught by the terrible DX that is almost natural to serverless IMO.
I'd argue serverless handles those cases even better. SQS for queueing and Kinesis for streaming have you pretty much covered. Much easier to manage those than setting up a fleet of workers that are all long polling for messages and managing heartbeat signals or routing to a DLQ manually.
Here the OP kind of got caught by the terrible DX that is almost natural to serverless IMO.