Just got some AirTags, great device. Can't live without it now.
You forgot the legendary iPod.
Personally, I recommend that you add it - even though it is no longer manufactured, marketed, or sold.
Many of us would never have been introduced to Apple devices, or arrived at the world of Apple without the gateway to Apple that the iPod supplied.
Anyway, I still have an iPod, and could not live without it, or an mp3 player. (No, the Cloud is not for me).
You will find many on these threads (of a more mature demographic, granted), who lament the passing of the iPod, and who adored the iPod Nano (a gorgeous and exceedingly portable device).
Moreover, I love my MBA (now, that is a device I could never do without, and is a device that should also be added to your list, for this is very much still extant in Apple's one-up).
Yes, I know that you define your thread as "important devices" while also "assuming (everyone has) an iPhone and a Mac". I'd add them: They are what one would regard as important, utter necessities. Everything else on your list is optional, perhaps desirable (although not by me), found under the "optional extra" heading.
Mind you, while I love my MBA (and it surprises me that it has not made your list), I am rather struck by the fact that none of the other items on your list - not one - would find a place on any my own personal list of "important" devices.