I think that a certain degree of caution is required here in the way we classify packages. While some people may consider
ifthen obsolete, it is certainly not marked officially as obsolete.
Compare ifthen's CTAN page with subfigure's.
This is not to say that there are not often better options, but the existence of better alternatives does not, just in itself, render a package obsolete.
Compare the case of packages for handling sub-figures.
subfigure is definitely obsolete, but this leaves several other options, including both
subcaption. In very many cases, the latter is preferable to the former - certainly it is more powerful, it works well with the powerful
caption package etc. But that does not render
Something being obsolete means, to me, that there is good reason for me to update existing code (e.g. packages or classes for which I'm responsible) even if there are no obvious problems with it. If my code includes the use of things like
\sf in a LaTeX document, or loads
subfigure, I really should do something about that if it is at all practical to do so.
But there is not the same kind of reason for me to update code which loads
ifthen and so it would be misleading to describe these packages as 'obsolete'. They are not. Not yet, anyway.