Apple is making investments in OSX: Catalyst, T2 chip /security, Touch bar support, iPad mirroring, airplay, arm64 support (speculating), SwiftUI. Metal/GPUs. Core apps: logic pro, xcode, playgrounds and brining more iOS apps (news, stocks, apple tv app, apple arcade with subscriptions). I also suspect with arm64 will come better cameras (lidar perhaps), beefier GPUs and neural cores. all of this running on macOS.

What kind of investment do you think they need to make to be a threat with Windows? If you think they should be trying to "match" windows with things it does, it would be a bad strategy that isn't winnable. Throwing away money. At least with their current approach they are levaring strengths (verttical integration, mobile dominance, etc) to build something that could leapfrog windows one day. Especially if the user journeys that span into other products (hw accessories, phones, etc)