The most important interview skill, however, is being able to effectively communicate and present that wisdom, because otherwise the interviewer will not know you have it.

That is a skill a lot of developers practice way too little. It's also a skillset that is increasingly valuable if you want a promotion.

It's interesting how so many of the responses here assume that the skills people should keep sharp are narrow technical skills. I'd expect a developer to keep their technical skills sharp as part of their day to day job. That's not the most important reason to practice interviewing; the most important reason is to know how to sell those skills.

I know lots of techies dislike having to know to sell themselves, but the reality is that hiring managers can't read minds, so selling your skillset is part of the job, but one you don't use very often in many jobs.

I don’t believe in generalists. Everyone has interests and strengths that over time move them in a direction to specialization. To say one codes both the front end and back end of a web site is about as general as I’d accept.

Example, game developers and financial systems engineers have very little shared domain knowledge and would require a huge amount of context switching on the order of months.

Mobile engineers also rarely want to work on server code. The tooling, the languages, the UX, they don’t even intersect on a vin diagram. Tools like react-native try to work around this discrepancy, but it’s few and far between.

Perhaps your experience has only been in general problems?

I prefer to be specialist in some areas and generalist in the periphery. e.g. I am excellent in distributed systems, Networking and FS, and have decent knowledge of web services, aws and kubernetes. I don't have any idea about embedded systems, mobile development and have no intention of acquiring that.