#232363 was closed as a duplicate of #231224 but it is not. I cannot comment there because the bot has locked it.

#231224 is about configurationDefaults not applying correctly.
The request in #232363 is that YAML code completion works out of the box without users having to change their settings, or extensions having to forcefully change a users YAML settings for all YAML files.

The issue is that the grammar treats most entries as "string" and quickSuggestions are disabled for strings by default.

The proposal by @RedCMD is to enable quickSuggestions for strings in YAML by default like JSON does:

   "[json]": { 
     "editor.quickSuggestions": { 
       "strings": true 
     }, 

I think this is a reasonable fix so that YAML code completion works as users would expect.