I remember trying the demo and absolutely hating it because they had changed too much.
Finally decided to check out the full game years later as I've been having Mystery Dungeon on the brain lately, and I'm pleasantly surprised with this remake.

My initial reaction to the removal of the standard attack and the change from IQ skills to rare qualities was negative, but I've come to realize that these changes weren't all that bad. I really like the standard attack from the previous games as it gives you an option to conserve precious PP at the cost of earning less EXP. However, Rescue Team DX has the move upgrade mechanic from Gates to Infinity, which among other things increases PP after a move has been used enough times. In addition, PP Ups are not too uncommon as rescue rewards, and dungeons hand out Max Ethers like candy on halloween, which lets you recover all PP for a single move. All in all, the removal of the standard attack didn't have a significant impact on gameplay, even if I'd have preferred to still have access to it.
Rare qualities ended up being my favorite new addition, despite my initial reaction to them. Long gone are the days of chugging hundreds of gummies to earn IQ skills. Instead, Pokémon you recruit may have these rare qualities upon recruiting them, or you may gain one upon eating a gummy. These qualities are serious game changers and they affect the whole team, but each Pokémon may only have one at a time. One such quality allows for multi-hit moves to never miss. This is insane as the usually weak multi-hit moves are super strong in Mystery Dungeon in exchange for having low accuracy. This rare quality removes this caveat, making them totally busted in non-boss encounters. Changing a rare quality is as easy as eating more gummies and hoping that you get the one you want. The ease of gaining these qualities in contrast to earning them like in the previous games may feel like cheating, but this has made me experiment with my team composition more, which I think is a good thing. Additionally, recruited Pokémon gain experience even if they don't go with you on rescues, which means that you'll have plenty of battle-ready Pokémon at all times. Considering how much of a grind it is to level up in these games, I consider this to be another great change to the series' formula.

In previous games, there could only be four Pokémon in your party at a time. A quirk of the Rescue Team games that isn't retained in the later games is that newly recruited Pokémon don't officially join you unless they leave the dungeon with you. If you recruit a Pokémon with a full party you'll have to send home a party member, say goodbye to a new recruit, or deny the newest recruit from joining. Rescue Team DX handles recruits in a similar way, as they still have to leave the dungeon in order to be properly recruited. However, this game allows the player to bring up to 3 Pokémon into a dungeon, but allows for up to 8 Pokémon to be in your party at any time, meaning that you can recruit up to an additional 7 new Pokémon in a dungeon this time around. I really like this as it serves as a way to recruit Pokémon more quickly, and having more Pokémon in your party at a time means more help inside dungeons. However, having a line of 8 Pokémon behind you can sometimes be problematic as Pokémon in the back may decide to engage in a battle that they have no possible way of winning, and the controllable party members are usually placed at the front of the line, meaning that the Pokémon engaging combat may be a lost cause, which can get annoying. And yeah, I said controllable party members in plural. Rescue Team DX allows you to change leaders on the fly, allowing you to switch control to any of the 3 Pokémon you brought with you into the dungeon. This is a great change, and the hunger mechanic seems to work around this as hunger depletes much faster, but hunger only goes down for the current leader.
Another small addition that I want to point out is the hole connecting your base and the Pelipper Post Office. This saves a lot of walking back and forth.

Additionally, I want to mention that the art style is pretty great. It seems to mimic the splash screens seen at the title menu, which I think is adorable. Every item has its own portrait now too, which I enjoy immensely. Seeing how the items are supposed to look is really neat.
I'm not sure how to feel about the music, however. The remastered soundtrack still retains the chiptune (?) bass of the original games which feels odd. I get what they were going for, as it captures the feel of the original OST, but it seems to defeat the purpose of remaking it. Also, the Mystery Dungeon OSTs love to use triangles, which sounds fine in the originals, but it's piercingly loud in DX which can ruin some of the songs.

There are tons of more changes in Rescue Team DX that I haven't even touched upon, but all in all, I think this is a great remake of a game that defined my childhood. I hope that this game sold well enough to warrant more Pokémon Mystery Dungeon titles in the future.

Overall, my main gripes with the game are,

- Tutorial could be better, there’s a lot going on here if you’re new to this style of game but I did enjoy the systems and manipulating fights the more I got comfortable with it. Maybe that’s more of a me problem.

- The story is a bit drawn out at points and some of these dungeons are LOOOOOONG.

- A lot of the customization of Pokémon in your party felt RNG dependent with the gummies and rare traits. You probably don’t need to mess with your Pokémon too much to beat the base game but I wasted a lot of materials trying to get rare traits I wanted and ultimately never did get exactly what I was looking for.

This was my first time experiencing a mystery dungeon game. Full disclosure, if I had played this game when it was originally released on the DS I would’ve been an insufferable Pokemon child (more than I already was). The personalities of all the different Pokémon here are just so wholesome. This game feels like it was created by fans of Pokémon, and it not being a mainline entry allows them to get whacky with talking Pokémon and I’m all here for it.

I totally get now why this is such a beloved series and I hope eventually an entirely new game is released for the Switch in the near future.