For me it has to be dealing with other developers who don’t want to keen with the times.
I don’t mind anyone deciding they don’t want to learn new things, for whatever reason.
But when you’re in a team if you feel that way it’s unreasonable to expect the whole team to stop developing their skills for you.

*keep with the times

Totally agreed

Agreed, but for completeness Id also mention that the reverse problem exists, that some devs are trying to push for the newest tech and approaches without considering project stability, readability, the time necessary to migrate to new frameworks/libraries, the code debt created by using a different approach across classes and projects.

There's somewhat of a golden ratio of when new stuff can start being used throughout a project or a company.