There are many times being a completist can be a pain, and playing through the Dr. Mario series has definitely not been the most entertaining experience. The series seems to make an appearance on every Nintendo platform with minimal changes, and so I wasn't particularly expecting much from Dr. Mario World, its smartphone iteration, released this past July.
I'm happy to report that I've been proven wrong, and the gameplay has actually the evolved the most since, well, probably any iteration. Unlike all the previous sequels, rather than farming the game out to a minor developer, Nintendo had their main group develop the title, and it shows. The game is structured pretty much the same as any number of match 3 mobile games such as Candy Crush, with added gacha mechanics and a versus mode. The core gameplay adds a new mechanic where you use touch mechanics to move blocks anywhere that they can fit, including halves of blocks. This change makes the game much more active and satisfying, as it basically does away with the basic and fairly lame chain mechanics from the previous games. The gacha component isn't too intrusive, and you roll for doctors or assistants. The doctors' specials are unique, although I find myself only alternating between two regularly (Peach and Wendy). Even without paying it didn't take me too long to get enough free rolls to build up a flexible roster, and the game also gives out items (which you can use to get past particuarly tricky stages) pretty regularly. A lot of the assistants seem fairly redundant, but I'm used to gacha games so those mechanics don't bother me too much.
In addition to the improved core mechanics, the game has also added a lot of twists to the stages, including bricks you have to break, viruses inside bubbles that sink according to gravity, and stages that continuously add more viruses. It's been prety straightforward to get through stages, with the exception of the timed stages which seem designed to force you to pony up cash to beat. The versus mode is fast-paced and enjoyable, and the daily missions and special events (e.g. special stages or goals with rewards) add a little bit of purpose.
All in all Dr. Mario World is a solid release and well worth a download. At its core it's still a match 3 game, though, and I doubt I'll be ponying up any real cash for it, but I've been playing it semi-regularly since its release and plan on continuing to do so. Even with all its updates it's not the most innovative game in the world, but it's one of the most enjoyable of its type that I've played.