Remember, Go was developed at Google - jokingly, while waiting for stuff to compile. They deal with tens of millions of lines of C++ written by thousands of engineers with varying skill levels and career paths. The advancedness of C++ did not reduce the compile times or readability of the code. At those scales you can't rely on being familiar with a particular section of code; you need to be able to drop in anywhere and know what's going on, without having to learn which subset of the advanced language they used for that particular feature.
Go is not advanced by design.
As for maintainability, it's not clear to me that reams of imperative code is easier to maintain than something terse and declarative. In fact, probably the opposite.
Go made a lot of odd choices from a language design perspective. It's pretty much "C, but with better types and a garbage collector!"
It certainly has its usages and does some nice things. But at the same time, the obsession with compile speed has, IMO, has been a detriment to the language as a whole. We see this in the way generics ultimately entered go after years of causing problems by not existing from the get-go.
That's very strong language. Go was created by some smart people that have completely ignored programming language developments that happened after the 70's.