So, you work in MK, and have never met people living in MK who work in OXF and CBG? That _is_ the point. The lack of a good transport option is one major reason why no (or few) couples would choose to live in MK to do this - it's a hard and unreliable hour by car to either destination from MK..
Then I realized you're actually describing my situation.. Live in Oxford, partner works in Oxford, my office is in Cambridge. Pre-covid I would do the journey once or twice a month - and half the trips driving, half by train - they were long days. I've cut back and go there far less now, but in any event, will have retired before the line reopens.
The Varsity Line shut a year before man stepped foot on the moon, and humans will be back there (2024) and perhaps have reached Mars (late 2030s, early 2040s) before the trains from Oxford to Cambridge return given current plans.
The reality is Cambridge is slightly further than London from MK.
Should we be *encouraging* more long distance commuting, which is bad for the environment, bad for people's health and in the case of the Eastern section of EWR going to cost getting on for £1.5bn which is unlikely to repay that outlay in the next century and that's before you factor in the running costs.