I mean, generics are kind of go's whipping boy. Lacking generics means you end up with copy/pasted code for utility functions that should be part of the go stdlib in virtually every project. It also means copy/pasted code for any data structure you might want to use that's fancier than an array.

Go's "simplicity" of error handling (read: lack of any actual error handling abstractions) means you don't get useful things like stack traces and have to manually grep through code for nested error messages. It also makes go code difficult to read at a glance, since virtually every statement winds up wrapped in repetitive error-handling code that doubles or even triples the amount of code in the happy path.

The error-handling pattern of using tuples, but no syntactical ability to operate on data within a tuple means you almost never have the ability to chain function calls like `a.b().c().d()`. Instead you have to manually unwrap the value and error, return if there's an error, call the next function, manually unwrap the value and error, ad nauseam. The "idiom" of gift-wrapping error messages is absurd — you are replacing machine-based exception handlers with expensive, slow, error-prone, and less-capable meat-based exception handlers.

Having a half-baked type system means you end up having to frequently write type-switches which are checked at runtime to do any sort of generic code. There's no functionality in the language to ensure that all possible options for that type switch are exhausted, so you are virtually guaranteed to get runtime bugs when a new type gets written and later is passed in.

Speaking of type switches, they interact poorly with go's indefensible decision to have interfaces implemented implicitly rather than explicitly. I have seen types get matched to the wrong typeswitch in producion code because a new method implemented on one type caused it to accidentally "implement" an interface used elsewhere in a typeswitch. Good luck ever catching this before it hits you in production.

Go's concurrency primitives are useful, but the lack of ability to abstract over them means that you have "advanced go concurrency patterns" dozens of lines long and involving multiple synchronization primitives for what amounts to `a | b | c` (https://gist.github.com/kachayev/21e7fe149bc5ae0bd878). God help you if you want to implement something like parallel map. God help you if you want to implement something like parallel map for n > 1 types.

Go requires you to manually remember to release resources you've acquired with `defer`, instead of sanely having There is no capacity in the language to enforce that you've done so, and it is virtually impossible to find e.g., a missing `defer fd.Close()` in a large code base. God help you if you leak file descriptors and need to track down the source.

Go's inability to perform any meaningful abstractions also means that you have to know all the details of code you import. It's difficult to make code a black box. Case in point: to do something as painfully simple as reading a file, you need to import bufio, io, io/util, and os.

During the course of writing this post, I forgot more examples than I listed — I literally could not remember them all in my head as I was writing them down. This isn't simplicity, this is utter madness.