That argument comes down to the scalability of RabbitMQ or one's database, both of which can scale fairly well, but require tuning. In the absolute worst case, one would have to use a distributed cloud database, e.g. AWS Aurora or AWS DynamoDB, otherwise a self-hosted one, e.g. TiDb or YugabyteDb, but far less than 1% of users would even need anything like it.

In the pre-AI era, the argument of using a third party tool or service even had some weight, but today, AI can even do much of the heavy work when pointed in the right direction wrt using the aforementioned. For the majority of users, a SQLite database will do the job.