In practice though a very large majority of applications are already expected to support a wide range of kernel versions and flavors, and require zero modificat

In practice though a very large majority of applications are already expected to support a wide range of kernel versions and flavors, and require zero modifications to do so because of Linux's outstanding track record of preserving reverse compatibility. So deploying an application as a container is a big improvement over shipping it as source or package, because instead of having to support any combination of library versions, distros and kernels, it only needs to worry about the kernel which is the easiest part.