I think there's a disadvantage with having languages designed solely by language design experts, and that is a tendency to over complicate things. They all understand it, and appreciate it's elegance, so it must be the best way.
To draw an analogy, consider the musical excesses of prog rock / jazz fusion. The musicians themselves may appreciate a Locrian scale played against an AbSus13th arpeggio , but the audience can easily end up excluded. Then a musically simple but catchy band like the Sex Pistols comes along and steals their audience.
I reckon languages need to be really really simple to understand, in order to become popular. For most people they're a tool, not an end in themselves.