You can use obsolete to describe anything that is no longer used in a particular way.
Examples:
Using an actual dictionary is becoming obsolete with the use of spell checkers and online dictionaries.
Video cassette recorders have become obsolete with the rise of DVD players and digital video recorders.
dinosaurs are obsolete.
The dictionary of 2001 was so OBSOLETE that the library was forced to take it off the shelves.
Inkwells are now obsolete since the ballpoint pen came into widespread use.
With the invention of the computer, typewriters were made obsolete.
Obsolete is an adjective.
Card readers are obsolete.
Vinyl records are virtually obsolete.
Todays technology will be obsolete in a few years time.
Maybe this'll work: "Placing your questions in the wrong category is quickly becoming an obsolete idea."
The computer I bought two years ago is already obsolete. That is an obsolete design and you can't find parts for it any more.
Obsolete
Nominating conventions are still held but have been obsolete for many years as those decisions are made in the primaries.