process inheritance was the best invention, because it models reality quite close. you dont have new things just sitting in an empty universe all alone and initialize everything themself from ... somewhere ... because everything is reset around them.

environment (in a broader sense, not just environment variables, but also CWD, file handles, uid/gid, sec context, namespaces) is there for a reason: to use. if you dont want your children processes to read the stdin in place of you, dont give it to them. it's the parent process responsibility to set up the env for the children.

although subprocesses are invented to do (some of) the parent's job by delegating smaller steps and leave the details to them. for example a http server would read the request (first) line, then delegate the rest of the input to a subprocess (worker) depending on who is free, who handles which type of request, etc. this is original idea behind inheritance, IMO.