That's a bit much. Type inheritance has been a core abstraction in software development since before most working developers were born. We as a society know how to do this. The idea that one oddball new idea is a revolution that turns a "nightmare" into sunshine is way too hyperbolized.
Sum typing might be better! But frankly the jury is still out, and the impact is clearly going to be smaller than what you're imagining.
The new lowest level pls (zig, rust) have ditched class based inheritance. Higher level PLs are going more functional, to include JS, where entire frameworks are encouraging functional (not to mention how everyone complains about the opacity of trying to use inheritance in place of declarative i.e. Amazon CDK)
Sum typing might be better! But frankly the jury is still out, and the impact is clearly going to be smaller than what you're imagining.