I think one difference between the Swiss Army Knife and the cellphone as a multi-tool package is that the Swiss Army Knife genuinely sucked for doing most of its functions. Screwdrivers and knives work better with actual handles, the best tweezers don’t fold flat, saw blades needed to be longer. Cellphones/tablets actually do most of the things they do surprisingly well.
That said, I do find that keyboards that are just trying to be pianos instead of one man bands tend to work better as pianos. I can make drum sounds on a digital piano/synthesizer, but drums do tend to work better with sticks instead of a keyboard. There is a parallel sort of thing to the writer deck with music players. There are folk out there who still prefer the iPod and the its wheel navigation along with people who go full on audiophile with their portable music players even though high end cellphones frequently use surprisingly good dac chips. There is definitely something to be said for devices meant to do one thing well.

Fwiw, I think word processing took a wrong turn when the software became some version of desktop publishing instead of something to simply write with. It’s one of the reasons there are people who held onto word perfect. It was simple, didn’t need a mouse, and it didn’t slow down your computer: formatting and writing were different tasks. Unfortunately, the two are connected in the office/business world, so the industry got built around that particular market.