People find this stuff exciting because most of our industry works on systems that are at least ten years behind the state of the art. A good example is HDFS, an extremely bad likeness of GFS which itself wasn't great and died ten years ago. If you describe Colossus/D in detail many people in our industry will think it's really amazing, but of course that's more than ten years old now. Many people will choose HDFS for new systems in new designs, today. You can spend your whole career without getting so much as a whiff of the state of the art.
I would say that a distributed filesystem is a solution looking for a problem in most cases. Amazon S3 or Google Cloud Storage address some use cases, and Google Cloud BigTable is a direct drop-in replacement compatible with the HBase API but having dramatically better performance and reliability. There are other use cases that have other alternatives, it all depends on what you plan to do with the data on the filesystem, how far you need to scale it, and whether you clients are in your own datacenters or in vendor clouds.
