One of the ways Jobs created a company that could grow towards a trillion dollar valuation was by having them *NOT* waste effort always looking back and keep supporting legacy stuff (Apple II/III,Lisa,Newton,68k,PPC,floppy drives, etc.), but always have the team look forward.
IMHO, trying hard to maintain a legacy code base is a major reason why MS is out of the mobile phone business and ends up with so many more exploits discovered in Windows. At some point you have to dump old code, or the returns become negative (unless, like some open source, a lot of the labor is free).
In spite of that, the latest iOS still runs on an iPhone 5s, and macOS on 6+ year old MacBooks.