Is the CRT still relevant when introducing display hardware
I haven't taught about analog television but thanks to my gaming related experience (both as a gamer and game development trainer) I know that the topic of horizontal and vertical sync is very important for understanding one of the more core things of computer science, the display. Further, I am all about the cutting edge stuff. 

Yet, when it comes to getting the concepts of display, I am all for going to the roots, and CRT is by far the easiest way to explain these things. So, to answer your question, yes, the analogy is still relevant. And going further, It will and continue to be the starting point for studying this display stuff.

Eventually, you will have to upgrade to modern screen but CRT is definitely the go point on the table.