Relational databases are tools to be used where it makes sense. NoSQL tables are tools. Graph databases are tools. Configuration files are tools.
Given your statement, Linux’s entire configuration footprint should be in a relational database.
As any good architect will say in response to a design question, “It depends.”
MSA’s aren’t a panacea either. Event Streams are an interesting development and new patterns are likely to emerge.
But today? I’d focus on reducing complexity with domain-driven design and choosing patterns that enable agility and support separation of concerns. MSA fits very well into that philosophy.