I agree with IGN's review. One of the dumbest things about 3D World are the lives. If you play multiplayer especially it just gets in the way over and over. Every person I know quickly sets up an unlimited jump on world 1-2 and gets 200 lives, then goes about playing the game. The fact that everyone I know immediately gets 200 lives before playing, enough said about how "lives" in 3D World doesn't make sense...
It also only takes a few hours to beat with my friend.
The new content doesn't have the co-op support of the old content either.
I find people interesting. For starters my nine year old twin girls have made it to level 4 without having to worry about lives... but full grown adults, whom are suppose to be hardcore gamers, need 200 lives? I also find it odd people are worried about lives. For starters the game saves after each level, literally after each level (not world, but level). And when playing if a player runs out lives, they simply reappear with 5 more lives per character. So if you are playing 4 player, 3 people die and there are no lives left, after the level the game saves and 15 lives are given out. I fully respect the opinions of others, but I simply do not get this one. What is the concern with running out of lives? Simply reappearing with more lives?
The game is shorter than many, but a few hours seems like a gross exaggeration unless you are speed running the game. Main story is 10 hours, with a completionists at 38 hours (https://howlongtobeat.com/game?id=9362).
I don't fully understand you coop comment. The new content isn't 4-player, but still supports coop. Frankly one of the reasons I love Nintendo, is they are the only ones left who support couch coop.
As for my opinion, the game is really good. The largest complaint I have (which IGN hit on) is after about world 3, 4 player is just a non go. Far too hectic with too much going on. Two player is optimal.