I don't know what is "ETL" meaning here, although SQLite does include a JSON extension to read/write JSON data too, so you can use SQL and JSON together if necessary.
Yes, if that is what you are trying to do, I think SQLite is good. SQLite command shell also has a .import command to read data from a file, and you can also import into a view and use triggers to process the data (this is something I have done). And there is also functions and virtual tables for JSON, and you can load extensions (written in C) to add additional functions, virtual tables, collations, etc. So for many cases, SQLite is useful.
