Like every game, for some people it clicks and for others, it doesn't. I don't think you're missing anything, it just didn't click with you.
Personally I love the game. I've had it since the first run (actually from that tiny run right after the first). I don't play it every day, and in fact, sometimes it can sit for a long time. And then I get the itch, and I start battling it again. The rules are not crazy deep, but I always enjoy them. It has a nice combination of easy things, and harder things to get all the way through the game. Sometimes I concentrate on just finishing Light Cycle, or Disc. And the added pressure of SOS is nice.
Quoted from vdojaq:
I recently sold my Tron Legacy and a couple of pinsiders had pm'd me with messages that I would regret, or I should re-think selling my Tron. No one was mean, they were just offers of friendly advice. While I am a big fan of the original Tron movie, the Legacy pinball just didn't do it for me. I do not miss it. I put my Stargate in the place of the Tron in my basement line-up and couldn't be happier.
And that is totally good. If Tron wasn't doing it for you, replacing it is the best option.