yes is heavyweight, SQLite for example isn't , but is kind the point you want database to use multiple formats, have acid compliance, json support, parallelism, easy debuggability, scalability, fault tolerance.
this are problems that you pay only little cost because 1 PostgreSQL database can scale to thousands or millions of users, and is more like a video editor you doesn't code directly in it, and data replication is difficult and expensive.
some people don't want have a server only for this and accept the drawbacks of not having a full database server, for example remoteok.