I saw an adult playing a 2DS in my doctor's office last year and I haven't done so since the GBA SP, mostly because the systems since aren't that portable to me. But if you want to, go for it. Fuck other people.
Don't buy any of them. Get Star Realms, it's a complete game in a box, it'll last you a long time. Free on Android and probably iOS too.
Best advice of the thread. I mentioned the same in a similar thread recently. It is on ios and PC/mac as well. The basic version is free but you only get AI battle and a campaign that way, for mp and a second campaign scenario you need to pay $5. That unlocks everything on all four platforms.