The point, I believe, is not about Linux kernel but rather "Linux userland". I'm sure you could replace "iOS" with "Android" and the meaning will stay the same: smartphone OSes go to great lengths to isolate apps and prevent them from messing with the user's data, while desktop Linux does not.
I hope the situation will change once Flatpak becomes more widespread and polished. On paper, it offers a comparable experience to smartphones — you get sandboxing with granular permissions, easy installation without messing with the command line, and so on. In practice, I had enough issues with Flatpak apps breaking in non-obvious ways to make me not recommend it to others. As a recent example, I tried using a JetBrains IDE from a Flatpak and spent quite a bit of time diagnosing issues with paths before resorting to Google and finding out that it's not supposed to work at all (https://intellij-support.jetbrains.com/hc/en-us/community/po...).
If you like Flatpak's issues you'll love Snap! The point about smartphone userlands is a good one. If the desktop modus operandi were similar to how APKs are used then I imagine Linux would have much better security. For now I think that only something like Qubes provides the security and isolation you want without subtly breaking things.
I hope the situation will change once Flatpak becomes more widespread and polished. On paper, it offers a comparable experience to smartphones — you get sandboxing with granular permissions, easy installation without messing with the command line, and so on. In practice, I had enough issues with Flatpak apps breaking in non-obvious ways to make me not recommend it to others. As a recent example, I tried using a JetBrains IDE from a Flatpak and spent quite a bit of time diagnosing issues with paths before resorting to Google and finding out that it's not supposed to work at all (https://intellij-support.jetbrains.com/hc/en-us/community/po...).