The original RFC for SFTP was written to actually be a simpler version of FTP. While v3 seems to be the standard and the final RFC was never ratified, SFTP is still FTP.
They are very different. SFTP isn't even textual, nor does it have separate control and data channels of FTP.
Are these exactly the same?:
https://www.ietf.org/rfc/rfc959.txt
https://datatracker.ietf.org/doc/html/draft-moonesamy-secsh-...
Note that SFTP is not a protocol for security transport / authentication. It doesn't do that. It assumes that you've already secured/authorized the channel with SSH. See section 1 of the RFC.
https://datatracker.ietf.org/doc/html/draft-ietf-secsh-filex...
Anecdotally, pestering a nontechnical buddy of mine to learn how to FTP games onto a ps3 gave him a headstart on a tech support role he got years later.
I'm some person in a suitable technical job somewhere. Yeah, FTP will be around for a long, long time. Will it be around forever? Not likely. Will it "soon disappear from the internet"? Even less likely.
Hooray for clickbait.