We love HDDR! We have been several times and everyone in my family across 4 generations considers it to be one of the best entertainment values in Disney, or anywhere, for that matter.
Try not to think of it as $300 on dinner. If you do, you'll definitely be disappointed. Think of it as evening entertainment that includes dinner and drinks. It is a dinner show, not just a meal. BTW, it's a corny, silly dinner show, which doesn't appeal to everyone.
As far as being shy about participating, there is not very much audience participation in this show at all. There's clapping and some singing along if you care to, but you won't be singled out. A player might come over to your table and ask where you're from, because in the beginning there's a song about where people come from. There is one embarrassing moment, where the "flirty" character singles out a man in the audience to tease...my husband was chosen the first time we took our kids, and my son, who was 5 at the time, took it quite literally and got pretty upset and protective of DH and me. He was OK when we explained she was just acting...precious memories.
Whether or not this show is appreciated is HIGHLY subjective, such a matter of taste. You should give it a try and decide for yourself. FWIW, we do enjoy the food...and the sangria. We always ask for more salad and drumsticks...and sangria.