Preface: I am a huge supporter of containerized distributed applications. It give me all sorts of nerd good feelings.
One of the biggest arguments for containerization of applications is that the application becomes portable. It no longer cares what it is running on, nor where, or how many. Windows server running a Unix FORTRAN application? No problem! Windows app running on a CentOS host? Done it! And while these are cool and nerd-awesome configurations. How often does an application actually change root host environments? If an application was/is made with .NET it is to leverage the advantages .NET has over other options. If RAILS, its for the advantages, if PHP, again, for the advantages over other offerings. To move away from those advantages negates the reason for selecting the solution.
On a related note; are we not simply replacing one type of vendor lock for a lock at another layer of abstraction?