The ETSI MANO framework has been under development since November 2012. It is a widely accepted solution for network virtualization. Despite its already long life the framework is still not only undergoing considerable changes such as extending support to containerized environments, but also lacks several features that are crucial for management and orchestration of network slices. The paper outlines the current issues of ETSI MANO in the context of generic network slicing, i.e. not limited to 5G networks only. The analysis covers the technical and business oriented issues. On the basis of the analysis we will propose the future evolution of the framework.