Being a systems programming language with a GC, following the footsteps of Algol68 RS, Mesa/Cedar, Oberon, Oberon-2, Component Pascal, Active Oberon, Sing#, M#,...

Coupled with powerful meta-programming capabilities, while having quite fast compilation times.

They just suffer from being a tiny community, so everything kind of improves slowly.

And Go and Rust stealing their thunder in terms of mind share.

While on the other extreme, Java and .NET keep improving their tooling and features for AOT compilation and low level programming, with OS platforms to go along.

It is not easy to find that sweet spot that makes a language take off.

Ruby was unknown for almost a decade until Rails came along, for example.