I had this problem for a long time. The root cause ended up being that the file C:\Program Files\dotnet\sdk\6.0.136\DotnetTools\dotnet-format\dotnet-format.deps.json had a reference to an older version of System.Text.Json. This was the file that was deciding which version would be used by the GenerateDeps task regardless of what version was referenced in the projects.

The solution was to uninstall the 6.0.136 SDK, install a newer one, and then do a Repair of Visual Studio using the Visual Studio Installer to fix the PATH variable.