It matters because it affects how many third party libraries are available and the number of other people that can understand and work on your code.
Object Pascal may have modern features, but that doesn't mean it is a modern language - nobody is going to start learning it now. Only people that have known it for years already will use it.
Object Pascal is very similar to C# in many ways. It isn't like a developer that has used Java or C# would have a hard time learning and understanding how to use it.
Re: modern languages: a language having modern features isn't a modern language, rather how popular it is at this moment is the most important aspect ? How did that work out for Python ? And where does PHP land using this criteria ? Is PHP better than Object Pascal because more people write PHP code ?
It _is_ a modern language, and people do start learning it when they get jobs that use it. It's just syntax, and it's a really good tool for certain jobs. You should give it a go with Lazarus IDE and see if you still feel that way.
Object Pascal may have modern features, but that doesn't mean it is a modern language - nobody is going to start learning it now. Only people that have known it for years already will use it.