I agree that it might have been better for that to be the TypeScript idiom, but it's not, due to the longer-standing popularity and concision and language-level support for enums. (Which couldn't have originally been designed to be lowered to symbols, because at the time symbols weren't widely-supported enough.)
Symbols are very well supported in TS today. You even get proper type enforcement and intellisense when using symbols as the names of methods and properties, for instance. Whether you should use them for enum-like purposes or not has more to do with how you want to use the values though. For instance using symbols for defining numeric protocol values doesn't make sense. Same for HTTP methods, where you are always ultimately passing a string down to the http client/server interfaces
