People expected massive fanservice but they got a great team party fighter with a Final Fantasy skin. Most people who played and enjoyed the original Dissidias didn't play it for the battle system but the fact you could beat up Squall with Kefka. NT was actually made as a game first and then as fanservice second, and that's a problem.
When the first news about it came out, most people were shocked to see you could only use one HP (damage-dealing) attack in battle, thinking they were dumbing it down even more; when in reality since it's a 3v3 game now, you have much more attacks and opportunities for setups and combos altogether as a team. Team composition, summon choice, attack choice depending on the arena size and obstacles, buff and debuff choices depending on the team composition itself, there's a lot to take in. So most FF fans trying out the game pick Cloud and try to play it 1v1, lose repeatedly, and give up. (Never mind the fact Cloud has one of the best HP attacks in the game currently.)
The other major issue is matchmaking. It's p2p, there are no dedicated servers, and it's utter shit. You get a bot match every other fight. It's unclear whether this is a technical issue, or there's simply not enough people playing ranked. (Of course, you're paying for this privilege with PS+, don't forget.) Lobbies are regularly up, there are communities and player run tournaments, even officially backed ones, but it's few and far between, there's like 2-3 teams that are regularly at top. The whole e-sports angle is flimsy. The game is very popular in glorious Nippon arcades, but the push overseas has been pathetic.
Of course, all this means there's no real singleplayer content. You have a story mode that's basically nothing, annoying summon fights and a pointless arcade mode where you can abuse the AI. At least there are no microtransactions to kike around. It's a shame, because the game itself is very fun if you find enough people, the characters are really well balanced and they've been updating the game regularly. To answer your question: Dissidia 012 is still very fun to play, lots of stuff to do (it includes the original Dissidia so no need to play that one), and if you have an itch to keep playing after that, get NT on sale somewhere or rent it, YMMV.