Costly: yes. Why not use another language? I think it's a perfectly valid question for that guy to ask. My personal opinion on "Why not use another language"

Costly: yes. Why not use another language? I think it's a perfectly valid question for that guy to ask. My personal opinion on "Why not use another language" is a bit different though: Adopting a different language might make sense – not necessarily for technical reasons but for cultural. The technical issues could have been addressed in time, and the language would be in a much better situation today. The fact that the technical issues have not been addressed for such a long time shows a clear lack of leadership and focus. I think these cultural issues are a bigger problem than the technical issues. You can fix code, but you can't fix people.