Your advice basically tells them to get out of JS development because businesses continually hitch themselves to <JS framework of the year>.

This stuff comes up in interviews. Trying to avoid answering direct questions about a framework and answering with "Well I can learn it really quickly because I'm a good vanilla JS Dev" doesn't fly all the time. If you can't answer direct questions about a framework, they will pass on you if they get someone who can answer those questions.

It has nothing to do with marketing yourself.