It isnt sarcasm. I don't really find a case that a database that has it's own query language like SQL is needed. It won't be different than storing a JSON file and filter the content with a for loop, the dev (e.g. me) will be returning a JSON on REST API at the end. A query language may be a good thing if you are working in a team, thats it. SQL is indeed isnt a good thing.
Um, so your use cases are extremely narrow and limited. That's an astonising failure of imagination and a lack of understanding of real-world computer systems if you cannot understand why people have a real need of both the power of SQL and the performance of RDBMSs.
PostGIS is an extension of PostgreSQL. It claims that it has some geography features. I think it is not really related with a database. It brings only a function (HAVERSINE) that gets distance of two points on earth. It is couple of lines of code. It is not really a software project, but a detail about how the earth coordinates are calculated, and I think it is a total made up story. The real computed thing works like math.sqrt function.