That being said, cartridges were fast. The move away from cartridges was a wrong turn
I've kinda given up on physical games at this point. I held on for a long time, but the experience is just so bad now. They use the cheapest, flimsiest, most fragile plastic in the cases. You don't get a nice instruction manual anymore. And honestly, keeping a micro SD card in your system that can hold a handful of games is more convenient than having to haul around a bunch of cartridges that can be lost.
I take solace in knowing that if I do still have a working Switch in 20 years and lose access to games I bought a long time ago, hopefully the hackers/pirates will have a method for me to play them again.
You've been paying attention to the wrong sources for information about NAND flash. A new Switch cartridge will have many years of reliable data retention, even just sitting on a shelf. Data retention only starts to become a concern for SSDs that have used up most of their write endurance; a Switch cartridge is mostly treated as ROM and only written to once.
I've read about people's 3DS cartridges already failing just sitting on a shelf.
Cartridges were also crazy expensive. A N64 cartridge cost about $30 to manufacture with a capacity of 8MB, whereas a PS1 CD-ROM was closer to a $1 manufacturing cost, with a capacity of 700MB. That's $3.75/MB versus $0.0014/MB - over 2600x more expensive!
Without optical media most games from the late 90s & 2000s would've been impossible to make - especially once it got to the DVD era.