To be fair the MEB platform is "all new"in a lot of ways and supposed to serve as a foot in the door as an adaptable foundation on which to build a compact, a SUV, a minivan, etc., and also be adaptable to meet the needs of the premium segment.
They could have gutted a Tiguan but they had already done that with the Golf, and were wanting to build off of that learned experience, so they wouldn't be trapped in old architecture – like the Kia eNiro or Volvo XC40 recharge. A clean sheet modular platform is so much more efficient (cost and design-wise, but maybe even electrically).
My impression where they went wrong is they didn't go far enough. As a shortcut they relied on existing modules and tried to wrap the code that drives them into their new system, and that's largely what's responsible for system lag, difficulty to update, integration, and bugs. But it was expedient and got the product to market!
I'm sure VW wishes they could walk back some of those early platform decisions that have proven to be mistakes.