The upthread comment isn't commenting on the existence of the package manager by the coverage of the ecosystem; every language has an ecosystem, but they aren't all equivalent.
I doubt the Ruby ecosystem is the largest out here. In terms of packages, npm more than 1 million, Maven Central (Java) 438k, PyPi (Python) 336k, Packagist (PHP) 323k, NuGet (C#) 260k, CPAN (Perl) 202k, Ruby has 170k gems, Rust 70k, Elixir 16k, Haskell 16k OCaml 3445. I couldn't find information for Go, and nothing specific for Scala and Clojure. Out of those the most comparable are Java, Python, PHP and C# due to the existance of Spring, Python, Laravel and ASP.NET competing against Rails. All of them have a bigger ecosystem compared to Ruby. In terms of scripting languages, Perl, Python and JS all have bigger ecosystems.
Of course you could reply about the quality of packages, but first, that's moving the goalposts, and second, why would the Ruby ecosystem be any better?
Package number is not enough. For example, .NET’s BCL is probably the largest of all the languages you shown where the other ecosystems would have to provide what it covers.
I don't think what you are saying holds. For instance, 32k [0] is just where intersection of both .NET frameworkd (Win only) and .NET Core (cross plat). If you want to see in total, this is a rough estimation, 634k APIs [1]. I don't know how much of that is .NET core only.
Come on, I already talked about that moving the goalposts things. Ruby is mostly used for monolithic web developement, and then scripts. This is covered by bigger ecosystems.
