There's been only one release per year in the past so you can't fault anyone to think the project is dead.
Why? It has regular releases including one in 2021. That looks like the opposite of dead to me. The only time there were more common releases, was 2018 when it was new, so the release page by itself screams "mature and stable".
The next Drill release will happen before the end of the year and also promises to be a big one. Some significant improvements are major rewrites of the Mongo connector, the ability to write to JDBC data sources, an Iceberg reader, Parquet updates and more.
reports of the death of the English language are increasing.
Drill is one of those technologies that people don't think to turn to today if they're starting a new project.
What does Drill offer that would make it out-compete the other candidates for a fresh new project?
Bottom line, a user can unzip Drill and with very minimal work, explore their data no matter where it is, with minimal config. This works as well on a laptop as a big cluster.
So for my use case this really fits and I guess it will be for others.
Be aware, there is no such thing as schemaless, Drill is schema on-read and if your files contain changing schemas, it is painful to workaround all the errors you face. JSON is too ambiguous when it comes to types.
The other issue I've seen is lacking documentation. I've been a Drill committer for several years and co-authored the O'Reilly book, Learning Apache Drill. I'm STILL finding undocumented functionality in Drill.