Please put fewer things in new language designs, not more. I say this on the slim chance it takes, and simpler designs are seen. I'll try to make my point briefly; note this is also what I think a design should do: make points briefly. First I'll make a comment on Rust. Then I'll offer to argue for simplicity in a language you talk about here if you want.

My guess is Golang folks will win, because Rob Pike gets the less idea. To compete Rust folks must go small, not big, so a language lawyer can explain in simple terms and still be correct. All I want is for things not to suck. I don't have an agenda to sell Go or Rust, I just think competition is good. So I don't want Rust folks to lose.

Rust folks have a clear disadvantage when more folks are involved in design: getting complex is often how smart folks compete, even when this loses the game for a group, as individuals win prestige for themselves in isolation. In game theory terms, folks betray long term global goals to get short term local reward. (Actually, there are several incentives to be bad; some folks like a priesthood model where complexity offers future job security in the understanding bottleneck. But this isn't as big a problem as complexity smelling good right now in arguments.)

Compare with C++: it got more complex over time, and adding new complexity is going strong. Folks who want a low level language must abandon it, because committee direction is toward high level. I used C++ from 1990 to 2010, but the direction of 2011 designs showed me I need to go elsewhere when I need runtime control. Or compare with Scheme, especially when it comes to the way R6 differed from R5. (I haven't look at recent Scheme efforts.) If you want design to be simple, it must be a goal. It won't happen accidentally when more than a few hands get involved.

How do you know when it's simple enough? There's an empirical test. Write down rules, give them to a fresh newcomer of mean ability and intelligence, and see if they can apply and defend them in various cases — especially when attacked by a bright lover of complexity. Your average practitioner should be able to say, "The simple rule here dictates solution X to your wicked problem Y." You did it right when this can occur. You did it wrong when it requires an expert to adjudicate normal discussion. It's a design smell if any part requires an expert to grasp. Another design smell: you grasped it last week, but not today.

Boil things down to basic definitions where they work when applied to complex cases. If you're so smart, you should be able to do this, right? Ask others for help when you want to know if it's simple now, because your perspective is suspect. Be agreeable to other folks rewriting your rules so they get easier to learn and apply. Tease folks who try to make things harder to understand because it makes them look good. You and your children are going to end up driving a car controlled by software developed by non rocket scientists. Ease up on them.