There was no Autosave feature in earlier versions of Word! Rather, there was, and still is, a facility that saves "AutoRecover" information at an interval that can be set by the user. In the event that the Word program terminates in an abnormal manner,
that "AutoRecover" information is used to recover a copy of a document in the state that it was in when the last "AutoRecover" save was made.
The default "AutoRecover" save interval is 10 minutes and it is correct that significantly reducing that interval can have a detrimental effect on the performance of Word as normal processing is interrupted when that save is taking place.
In earlier versions of Word, the "AutoRecover" save version was deleted when the file was closed.
There is NOTHING for Microsoft to bring back! The original facility is still there in a slightly enhanced form as there is now a box under File>Options>Save that, if checked, will "Keep the last AutoRecovered version if I close without saving".