I think it’s pretty much just about it being a vector for malware. Since it’s autorunning by itself, I think it’s pretty unsafe when inserting USB drives and CDs or DVDs in case the inserted device is infected. I guess autorun/autoplay isn’t dangerous on its own, but combined with an infected drive you’re basically gonna accept possible malware with open arms lol

You can disable autoplay easily in settings, but USB are usually much worse than CDs because you can easily add more stuff there and modify it.
Biggest problem I have with USB drives is that they can go crazy with no specific reason and make all data unusable.
That's a good point. There is a similar problem with smartphones, especially android ones, where we have many producers and many OS versions, distributed by phone producer. Sooner or later they stop publishing a new OS updates, then users should think twice if still want to use banking app etc. on not-updated phone.
I am not a fan of iPhones but they have longest support from all smartphones, and for Android devices Samsung and Pixels are one of the best with longest support.
Everything else is trash and I would not waste money on this devices, but maybe they can be used as alternative offline wallets for bitcoin (if done correctly).