We play mostly theme decks and we like it.
The two ultra prism decks are difficult to play optimally. Trying to reach that level probably takes 100s of games. It's a worthwile goal imho. Sure, most matches are decided by RNG (start, draws, prizes, coin flips). They're usually quick matches. But the 10-20% remaining games are mostly skill-based, in the sense that if a player misplays or chooses a route with lower odds then the other has a rather high chance of winning.
It won't get old for me until those “I lost because I did this and should have done that” moments disappear. Those are worthwhile losses.
I hope the next decks will be at the same power level. This will make optimal playing even more difficult.
We'd also like to play non-newest theme decks for a change. I've made a suggestion that it's better to wait longer and meet a deck with a comparable power level. No user replied, nobody upvoted.
This would solve the problem though. If users were prompted with some message e.g. “opponents with a similar deck couldn't be found, wait longer or click here to be matched with any opponent”, this would act like an on-demand separate queue.
tl;dr The newest decks are great, theme play is not being killed, but matchmaking should be improved.