I hope I didn't make anyone feel like their opinion was invalidated. Maybe it's the fact that this is one of those games that has such a wide range of responses. You can see it in the review scores. On one hand, you have people who scored the game a 4, while others scored it a 9, and then everything in between.
Instead of trying to imagine what negatives others see in the game, I'll talk about what I think are positives. The things that have stood out to me that I think make this game work:
-Control. This is the first time that it feels like Sonic can be manipulated the way I want. Granted, it has to be learned first. It really only took me about two levels to really get the hang of it. But once you know, it feels really good. I was especially impressed on the fast 3D stages because there are some of those tube designs where it feels like a lot of things are happening at once, but somehow it manages to work. The fact that Sonic can do a 90 degree turn on a dime and still be controllable as well. It doesn't sound like it should work, but it does. I think what made Sonic a pain to control before was the fact that turning was too slow, or too random, or too finicky or something. Also the parkour is great. This is a boon to Sonic games, and I hope that Sega never gets rid of it. Almost all of the cheap deaths can be avoided if you are decent with the parkour system. It also opens up the possibilities to get secrets. I hope Sega takes more advantage of this in the future.
-Graphics and performance. Seriously, this is a big improvement over Generations and Colors, excluding the PC version of Generations. Both games, as far as I remember, ran at a lower frame rate and the console version of Generations in particular felt sloppy because of it. Go back and play it, it just doesn't feel the same without a constant 60 fps. There are a few dips here and there in Lost World, but for the most part, it is impressively smooth.
-2d stages are fun. This shouldn't be a surprise for those who liked the 2D stages of Generations, which I thought were generally pretty decent. But I think they are better in Lost World. I think it has to do mainly with the new control system. Being able to hang on ledges and have different ways to run and walk and spin dash adds a lot of variety. I was impressed to see quality platforming levels here.
-Overall polish. The game generally just feels polished, besides a few minor nitpicks like Wisp integration and inconsistency in the boss difficulties. Even then, everything is still fun. Most of the wisps have an alternate control. This is good, because if there wasn't, that would be a huge problem. The dig/rocket wisp doesn't work very well on the touch screen so I end up just controlling it with the analog. The aim was a little bit janky with the air rocket wisp. And so really, my only real gripe with the game is the inconsistency of the wisps. There was a wisp that was very similar to one of the effects in NiGHTS. You basically act as a magnet for other things, and then when you get to a certain spot, you rake in the points. I thought that was a cool throwback.
-the game is just simply fun. It's weird. But I am having more fun with this game than Mario Galaxy. I know that sounds strange. Mario Galaxy is a supremely polished game, and is the originator of the planet idea. But I think after completing the game, the idea just felt stale and the levels were too disjointed. I'm one of the people who likes the sandbox style Mario the most (Mario 64, Sunshine, etc).
So generally, for me, the lowest low points are even managable, while the highest highs are very fun and thrilling. I think this is a very good Sonic game, a good platformer, and shows lots of improvement in overall quality compared to previous Sonic games. I hope Sega keeps up with that at least.
EDIT: It's interesting, I just watched the GameExplain video and I think that's a pretty good assessment that fits with most people's experience. I still sincerely don't experience the frustration with this game that a lot of people are feeling. I dunno. It's weird.