Yeah, reading has gone downhill ... but that downhill process was happening before the smartphones.
And, if you consider that you don’t really have to read or write very well, with the smartphones and other smart devices, you might say that these smart devices help people who can’t read and write very well.
One time (the only time I’ve personally come across it) I came into contact with a young person (about 18 or so at the time, back in 1999) who really could not read. It surprised me! But he somehow managed to squeak by, and on the computer, using instant messaging. It was strange!