C#: (this was my primary language and had been for a number of years now).
Java: (this was my other primary before switching to C#)
Both of these have horrible run-time independent pieces that need to be configured on each machine I deploy to. About half my apps need to be distributed to end users. It's tough enough to deal with the applications themselves but adding a separate runtime to the mix is what I'm moving away from. Also, C# and Java are just too kitchen sink these days. Unlike many, I don't have problems with breaking language changes. They're annoying but I'll recode. Having to deal with all the baggage these languages have is the main reason I looked for a new primary language in the first place.

Elixir:
The BEAM runtime, if I'm going to be fair to C# and Java.
Elixir is the most elegant language I've seen in years. I really wanted to like it. I purchased all the available books and really dove in. But then I stumbled on the soft spot of number crunching essentially being left out of the language at the lowest level! That's a tough one to get over as a couple applications I have do lots of financial "what if" calculations. Also Phoenix has an annoying list of dependencies (Node???) and a complex configuration compared to Go.

D:
I wanted this to be my primary language after reading Andrei's book when it first came out. Unfortunately D wasn't there yet (this was during the shift from D1 to D2). And after D2 solidified as "D" it has has been moving towards memory layout, CTFE, removing garbage collection, and other lower level stuff that I just don't care about. All of my applications are at a business level and dealing with memory and performance optimization is just not something I am ever concerned about.

Rust:
Rust sits at an even lower level than D. I really like the higher level ideas and syntax but I absolutely don't want to think about ownership issues. If that part of the language were removed Rust would be pretty ideal. But then it wouldn't be Rust. Manually controlling the ownership process is a core part of the language and would be pretty hard to change.

Python:
Bad deployment situation on Windows. But also I've decided I really prefer the compile time type checking. And while I notice the speed issue I can't really say it's a problem for the applications I code. But I do like the blazing speed of Go and the other compile to the machine level languages.

Dart:
Hits on most every item on my checklist. But again, a bad deployment situation. And Dart's focus has shifted towards the JavaScript side and away from a general application language and server side language.

Nim:
I'll add Nim because it shows so much promise. I've followed Nim for years, support them on Bounty Source, pre-ordered the book, and keep up with progress. However it's got probably close to a year before 1.0 and probably three or four years before it is as production ready as Go is now. But all in all it's shaping up to really hit the sweet spot for business level apps at a compile to binary level.

Honestly, Go has so much going for it that the items I find missing just aren't nearly enough to stop using it. But, for me, it could be so much better with just a half dozen additions. It's frustrating to see it so stagnant after just being born.