Our backend is primarily in Scala and has been for over a decade. My take is that Scala 2 -> 3 was a massive hit to the language's momentum. It came at a time when the language's popularity was waning and it had all the same challenges that other major language version changes tend to have. Migrating's been quite challenging. Tooling, which was already a challenge for the language, got worse because it was split between Scala 2 and 3.

The language was deliberate about providing backwards and forwards compatibility between 2 and 3, but they didn't have a good story for macros. Yes, macros were experimental, but the ecosystem relied on them very heavily. This meant that your 3rd party dependencies likely hadn't migrated to Scala 3. If they had, things got complicated because you had to deal with two macro systems.

After many years the tooling is finally catching up and many 3rd party dependencies are available in Scala 3. That said, it's taken years and years. I think during those years many companies migrated to other languages or put a moratorium on new projects in Scala.

My impression is that, rightly or wrongly, it developed a bit of a negative reputation in various ways - too esoteric, slow builds, toxic community, etc. - so people stayed away from it.

And meanwhile, Java the language improved and Kotlin came along as (arguably) the better better Java, so there became less of a need for it.

I wonder how you see 10x more Clojure news.

Scala's usage is stagnant or declining, but Clojure has always been tiny in comparison. It doesn't even register in most rankings (TIOBE, StackOverflow) which is also confirmed by hard numbers e.g. GitHub statistics.

Kotlin seems to have eaten Scala's lunch, for many organizations in the "JVM-but-not-Java" camp.

Also, non-backwards-compatible language changes fragmented the Scala ecosystem. Combined with the general trend of functional programming hype somewhat dying down in recent years.