yserb, no one thought of it as a huge holiday until present-day chabad. They make big deals out of all sorts of things, including “hakhel.” And of course they think all of us need to celebrate it, because it’s not chabad, but rather Judaism that makes a big deal out of it, and don’t you want to follow Judaism?
they expect everyone else to follow them, in every regard, nothing new here.
I made a nice bracha li’ilui nishmas the maggid, and I don’t say tachanun; that’s about it