Most of the criticisms you may have heard about this game do indeed apply. It is simplistic, there is not a strategy element like in the main series games, and it is pretty repetitive. However, you do get to guide hang out with all of your favorite pikmin again (except I have yet to encounter the white ones), and if you play toward the goal of completing all goals for an area, then it can be quite fun and challenging.
Most areas have at least two challenges that are optional and do not affect your ability to beat the game. The first challenge is to first discover all 20 pikmin and then to not let any of them die during the level. The second challenge is to discover the hidden artifacts in the levels and retrieve them. Attempting to complete these challenges has caused me to place most levels at least 2 times so far, some even more. Some levels also have secret exits which open an extra level for you.
Gameplay is repetitive, but still fun. You tap where you want Olimar to throw the pikmin in a side scrolling universe, and you move Olimar with the circle pad to try to find the exit(s), all the while collecting a little sparklium to help your ship take off and go home. There are 9 sectors. I have not completed them all yet, but according to online guides, there are 5 levels and a boss battle in the first 8 sectors and one boss battle in the 9th. There is no strategy element to speak of in this gameplay, but there is a puzzle solving, and a new element introduced of Olimar having a jetpack. So at times he can jump and fly to place the pikmin cannot go and you must solve a puzzle without them or in a new way other than just throwing them.
Amiibos are used in a fun way, but not in a very necessary way. If you have a bunch cluttering up your bathtub, then you can break them out for this. Each Sector has a couple of special one-screen puzzle levels that will unlock when an amiibo is scanned. The scanned amiibo (only Animal Crossing, Pikmin, Splatoon, and Mario Party ones are supported I believe) will appear in game as an artifact and you must figure out how to get the Pikmin or Olimar to collect it. If you do not have any amiibos, then the one made special for this game will act as a randomly chosen amiibo for you when it is scanned. I have not used this feature much, but it would seem all you really need is luck and the Pikmin amiibo for this game to unlock them all. As with all artifacts, there is a funny description unlocked when the amiibo is collected and catalogued. You could easily beat this game without the need for any amiibos, and the only thing you would miss are a couple of one-screen puzzles and a bunch of funny text which you could easily find and read on the internet. You can also use the special pikmin amiibo for this game to cheat in a level, by calling more pikmin to you once per level. So if you had 10 pikmin and accidentally killed 5 but you could not progress any further with only 5, then you could scan the amiibo and more would come to help (amount depends on the level of the amiibo), however, it is clear the game sees this as cheating, because it will not allow you to unlock the special challenge of rescuing all pikmin if you use the amiibo in a level.
Lastly, there is a minigame that is not very game like, in which you send the pikmin you have lead to the exit of each level into a top down environment and you leave them to harvest fire, water, crystals, grass, etc in an area and unlock more sparklium for you. It is a very slight attempt at a management sim, but it does provide yet another reason to replay certain levels if you are stockpiling a particular type of pikmin for harvesting purposes.
There is a demo for this, if you try it and you feel that you would want to repeat those actions over and over for roughly 40 levels, then this is definitely the game for you.