Super Mario Kart wasn't only an innovative and fresh title back on the SNES. It was a paint-by-numbers piece that every kart racer to follow would use for "inspiration." It was wild fun with warping mode-7 scaling and rotation that showed off what the system could do. However, 13 years is a long time, certainly enough to make the concept stale without change.
Mario Kart DS doesn't reinvent the genre. Whether or not there's actually anything left to insert is debatable, and long time fans should be happy. What this DS entry does is introduce, in a flawed manner, Nintendo's free Wi-Fi service, and it's hard to think of another Nintendo franchise that would fare better in this position.
It's immediately apparent how refined this fifth game is in the series. The controls are perfect, simplistic to the extreme and accessible to the masses. It's not possible for cornering to feel any easier than this. The eight riders (sadly, only four maximum online) rarely crowd the courses, and these are a mixture of new and old.
If it's so easy, that should put everyone on a level playing field. The introduction and focus on drifting is the change in the series that evolved over time, and it's what separates the newcomers from the experienced players. From the simple to execute drift, there's an opportunity to boost. When done right, it changes the flow of the race. It's also exploitable, and expect to be destroyed by some players online as their cheap tactics push them further into the lead and the only thing that can stop them is luck.
Luck is also the aspect of the game that has become apparent over the years. Yes, there is actual skill involved, but the items that litter the tracks are based on a simple system of catch up. When in the lead, that person will never see any items except a banana peel, fake item box, or a green turtle shell. The person in last will have the full array, including the ridiculously unstoppable bullet bill. This is more apparent here than it ever has been, and doesn't increase the enjoyment of the game's key online features at all.