|Think about Loose Coupling|
That's only if you do waterfall-style development, and if you have well-financed dev team.
How is that true? Does agile say that you requirements be never frozen?
And having a dog slow compiler frustrates people, and drives them away.
How big is your user base and how many have been driven away? There are slower tools, like Scala. Which many people have no problem in using. Mainly because they can atleast use it, instead of a product that isn't complete but promises to be. I guess you don't realize you have a literally zero user base, apart from a few people who like to write one liners on IRC or write toy programs to implement commonly known algorithms on Forums which no one takes seriously. Which explains why they are happy with a sub set of features. Because for most toy programs you don't need much, but the existing ones to run fine
Also, while Rakudo isn't feature complete, most user complaints these days concern performance and reliability, not features.
Also who are these users? Can you show us at least on serious use of Perl 6 in the wild? A big company, A start up? Anything?
C++ with gcc and clang, and C# with mono/roslyn, and java with OracleJVM/OpenJDK + javac. The compiler (and VM) developers spend quite some time optimizing for performance. Yet none of the languages are feature complete
They are incomplete in the same sense iPhone, or your TV is incomplete. It doesn't mean iPhone's or TV's aren't usable now. It only means they may get a few feature based on the competition they face in the future
Perl 6 is just incomplete. Its a bit like shipping an iPhone without a feature to store phone numbers. That's a very different kind of incompleteness than the former.