I would like a word -- and perhaps it exists already and it just eludes me at the moment -- which is a milder version of should. A word that means "Your life would probably be improved by doing these things, even though what you're doing now may also be good."
If we had such a word, it would make it easier to have "You should" conversations without people becoming offended. Our world may be great, but I think that a world with a word like that would be a little bit better.
2) What about "can"? It's not a drop-in replacement for "should", but it has a lot of what you're going for. "Non-programming skills every programmer _can_ have" is about aspiration not judgement, possibilities not failures.
For example, I've personally realized that management is not really my thing, but having done it for a while I understand better now where my ex-managers were coming from and feel that I'm now a better employee because of that. Same for design work, etc.
And frankly I wish other people did that too. Wouldn't it be great if your manager understood your explanation of why that "tiny" feature will actually take weeks, or the designer keeps potential code complexity in mind when designing something? I think this advice applies to everyone, not just programmers.
> Also, it's good to have some management and leadership skills.
It's good, but not everyone wants to be a leader, and if everyone led it would be chaos. You're not a failure for not getting promoted into management.
> A programmers aim shouldn't be to simply write good programs, rather it should be developing really great products.
Yes, but programmers can work on teams with great designers. They don't need to do all the jobs.
Every skill on this list is a skill that takes the place of something else in your life. There's simply a finite amount of time in each week, and if I want to get better at design does it mean that -- maybe I give up on guitar or baseball or something?
I encourage programmers to think about what they really want -- not just at work but in their life -- and remember that the loudest folk are also the strangest.