Learning From Old Tech
You can learn a ton of valuable things from looking at old technology.
However, beware FallingInLoveWithIdeas.
Where can I start?
Look at low-level systems that didn't win mindshare because they didn't have backwards compatibility. ISAs other than x86, for example.
Look at UI paradigms that need the entire platform to follow the metaphors. Oberon has an amazing concept of allowing system text to be interactive commands. Lisp systems had interpreters ("REPLs") where the visible value was still associated with the underling object. It wasn't just a string representation. Smalltalk systems historically had their own VCS and GUI.
Look at tools where the existing solution is ubiquitous and hard to replace. The string oriented shell is very limited on unix, but Powershell has some excellent ideas.
Is this a new problem?
No. The Unix Hater's Handbook was published in 1994, but many of its criticisms are still valid today!
(Examples: Unix lacks "logical command names, careful handling of dangerous commands, consistency in argument handling",
rm * is handled by the shell so
rm cannot do a sanity check,
man does not have standalone pages for shell built-ins)