Well, maybe I used to work with more complex data ...
Yes, that's exactly the point. I worked for 8 years for large companies in the logistics sector. We mainly used enterprise servers by Oracle, Sybase and Informix, which of course work on a higher level than SQLite, because they are highly configurable and come with huge performance and stability benefits for simultaneous write operations. For such case I would not work with SQLite and I think it would not even be possible.
But as long as I can run SteemWorld with my current setup, I will stick to SQLite. There is only one process that needs to write to the databases and I don't think that this will change in the near future. Re-indexing the data can be executed in a separate backup path without having any server downtime. Maybe at some point in future I will tell you that I needed to upgrade to a more complex engine, who knows :) For now it's working great.