When we worked with MacColl in the Critics group, he divided the work into two distinct parts.
The first was the voice - the 'toolbox', with which attempted to master all aspects of your voice so that you could handle virtually any song in the repertoire.
The second was making the song yours, analysing it to understand it thoroughly so you could identify with it to make it your own.
One without the other was short term and in the long run, unsatisfactory.
It was when you brought the two aspects together that the songs began to work for you and, if you put in the work, stayed with you forever (as I am now finding after decades of not singing regularly.
Jim Carroll