I’ve heard from authors that typing someone else’s entire novel helped them to understand the craft (and then they went on to write their own books, not based on the novels they typed).

And of course musicians learn other songs before they write their own.

But, copy/pasting an article, and then tweaking a few words to make it more unique, doesn’t seem like a great process for learning the journalism craft. At least not on the same level as the two examples I brought up.

to the non expert ear, Get Free sounds much much more similar to Creep, than Creep does to "The Air that I Breathe"

If the "groove", "feel", or chord progression of such a song is identical or substantially similar to the song you copied from, you could still be liable for copyright infringement per Williams v. Bridgeport Music (the "Blurred Lines" case).

Before you complain, note well that among black musicians the groove is the song, the melody being something of an afterthought -- the exact opposite of what prevails in the white concept of music and, in particular, historical understanding of copyright law. Black musicians have been trying to get acknowledgement of ownership of their grooves for decades.

In general, it's not a good idea to use someone else's song as a starting point. In most cases, the original composer is going to be able to establish some form of "substantial similarity" to make you liable for infringement; it will take radical transformation to avoid this.