> These tools' relative importance has declined over the last 15 years.
I would say to the contrary. There has been a flurry of new development on Emacs in the recent years initiated by a new generation of developers. New (and simpler) search and autocompletion frameworks (Ivy, vertico), native compilation of Elisp, the rise of Org and the advent of LSP clients (thx VScode). In the coming years Treesitter might render LSP obsolete some day. Exciting times ahead.
And what does it mean to be an old piece of software anyway?
Software may age but compared to hardware it has the advantage of being able to evolve. I hate it to break to you: Windows and Linux kernels are over 30 years old written in a language that was invented 50 years ago. The whole design principle of state of the art operating systems was invented in the 1970s. MS Office kernels are probably older than 30 years and the leading X86 platform looks back on an over 40 year old history. The first Python version was released back in 1991, that’s 30 years. JS almost has 27 years (1995 afir). Chrome BTW was released back in 2008, that’s already been 14 years. Safari‘s engine comes closer to 20 years.
Does it even make any sense to compare Emacs 29 with versions from the 80s?