I wrote a pretty in-depth review with a unit I was sent early this month. It's a fantastic presentation, the music is great, and the card game itself is simple enough that you can teach it on a single turn, but has surprising depth and strategy if you want to invest time into learning the cards.
But yes, the music is definitely just as an added bonus to the game. There's no skill or mechanics within the music composition itself.
DropMix GameZone Review
This game does look cool as hell. $100 seems steep plus another piece of plastic taking up room. I cant help but think it would have been much better as a digital game instead of a piece of plastic. Sell the game cards as dlc and put rare cards in crates like rocket league. Not sure why they went this route. Would have been a day 1 purchase if it was digital and cheaper.
So two points I want to touch on. I don't really think this counts as "another piece of plastic taking up room" since it's intended to be a board/card game, that you place back inside its box and on your shelf of other board games. I don't think this is supposed to live on your living room table, or propped up in your storage closet. Think of other large board games with hundreds of miniatures and environment pieces. At least DropMix has literally 0 set up. You take it out, turn on the app and boom, you're playing.
As far as pricing goes, I somewhat agree. It is pretty expensive. You only get 60 cards, which essentially means you get enough for four players to play 2v2. However, with that limited amount of cards, you run into similar mechanics and strategies, especially if you really only have to learn 15 cards (per person). Doubling that to 120 would have made subsequent back to back games a lot more interesting with more variety. As I noted in my review, I paid somehwere around 80 for Skylanders which came with three figures, an NFC reader and a fully fledged game, so a $100 for a card game, albeit an extremely cool one, is a little steep.
I definitely disagree with your suggestion about putting digital rare cards into loot boxes. The game is a definite money sink if you plan on buying every card pack, but at least I like knowing that spending 15 bucks will get me the entire set of cards. If this went the TCG route, I probably wouldn't have been that excited about growing my card collection later.