Angular 8 is over engineered, there are a million pieces that make the app work; any of which can and do break. With the code freeze by EOD, you're trying out different compiler options just so you can get the console error to stop and pass the build. There's this unfathomable love for typescript that is designed to dumbify the js dev population. For config, There's angular.json, tsconfig.json, webpack-config.json, tsconfig-app.json and package.json to start with.

There's @component, @inject, @injectable. And you also have to know @component inherits @directive.

And while you're ramping up with this don't forget ngc and ng-packgr. Check ng-cli version before compiling.

And yeah, do this before the next angular release, which is in next month.