For one - the error handling. Every codebase is filled with messy, hard to type:

if err != nil {
    ...
}

And it doesn’t even give you a stack trace to debug the problem when an error happens, apparently.

Second reason - it lacks many features that are generally available in most other languages. Generics is the big one, but thankfully they added them in last half a year or so. In general Golang’s design principle is to implement only the required minimum.

And probably most important - Go is owned by Google, aka the “all seeing eye of Sauron”. There was recently a big controversy with them proposing adding an on-by-default telemetry to the compiler. And with the recent trend of enremovedtification, I wouldn’t trust google or any other mega-corporation.