I think all thanks should be tailored to the person receiving those thanks.
If thanks have been given in person, it's not necessary at all to follow up with a car/letter/text/email.
One family member I know very well, we exchange thanks via text. that works for us, and others I exchange emails with.
It's extremely rare that I write thank you notes, as very few of the people who would send gifts are not connected via technology in some way.
Again, it's all about tailoring a response. And same for things like sympathy cards. It's all well trying to write a nice thoughtful letter, but as in the case of Mia4 and her friend, you have to judge whether it would be well received.
I personally prefer to receive thanks by email or phone call. Cards/letters, however well intentioned, are read and put straight into the recycling, as I think of them as an unnecessary use of paper.