as pointed out the ICAO flight plan is a world standard designed in the 1940s , ir was coded in such form that it could be transmitted quickly and most importantly, to be understood by every country on the globe.
How the flight plan is processed to fit the ATC system is a local decision . It can be done to just print strips , activate a basic flight plan processing system ,using off the shelf PCs , or using very sophisticated systems like the one currently used by NATS . And there is no standard for doing this .
Changing the flight plan format to the 21st century and defining a digital standard that every country ( including the US ) would accept and then retrofit to is being discussed and worked on since decades , and likely will take many more decades to see it implemented.
That said , a bug can always put down a complex system, the French 4Flight or Maastricht MADAP are as much if not more sophisticated systems than the NATS one , they.also do have such failures from time to time , but their various back up systems activate to enable a quasi transparent restart for the users . Why the back up did not work as ( hopefully) designed is the real issue , and why it took them so long to isolate the problem the other .
Focussing on a wrong flight plan , or a duplicate 5 letters waypoint , is not really the issue here , in my view at least as you can never be able to eliminate 100% of them .