Phones didn't take over as much as 3DS just dropped the ball. It was overly expensive, tiny, and had no games. Had they launched with a $150 2DS XL in winter 2011 they would have done way better. Glasses free 3D dragged the 3DS down in much the same way that the tablet controller dragged the Wii U down. Without either gimmick both the DS successor and the Wii U would have been affordable systems.
Super Mario World was rushed? They worked on that thing for 2-3 years. It was ready for launch, and IMO is one of the 5 masterpieces of the SNES. The other four being Chrono Trigger, Final Fantasy 6, Super Metroid, and A Link to the Past.
They worked on it 2 years while also working on Link to the Past. There is a 2 year gap between Mario 3 and World. There is a 4 year gap between Zelda 2 and Link to the Past. Considering that Mario World was the first game released on brand new technology, yeah it was rushed. Most people who lived through the NES and SNES eras will say that Mario 3 is better. Mario World mostly seems exceptional, because its the only new Mario game on the SNES.
Speaking personally, Mario 3 feels a lot more polished than Mario World. Mario World is too easy and isn't as densely packed with secrets like Mario 3. It's still a good game, not denying that, but it feels rushed.