On the app it says they don't know how engineering work is going to affect the timetable but otherwise seems to be final (though I agree they don't have a clue...!)
This was response from GTR (I'm going to reply as they didn't mention the misleading consultation):
Thank you for getting in touch regarding services from May 2018.
I was sorry to hear that you're unhappy with the forthcoming timetable changes in relation to services between Hertford North and London.
With passenger numbers doubling in 16 years, the allocated stop times at many stations are simply too short to reasonably account for those getting off and on. So at 75 stations trains will stop for longer
We have completely re-written the timetable to add in extra time at stations now needed for additional passengers to board. We've also reviewed all the intermediate running times between stations to make sure our timetable reflects reality. We know this sometimes means journeys are timetabled to take slightly longer in some circumstances but passengers will be able to rely on them.
In addition, many services currently have very short turnaround times at destination stations, so the slightest delay on the route means they don't start their return journey on time and the delay multiplies - the new timetable has increased turnaround times to help
We have done our best to produce a timetable that meets the needs of the majority of people who travel with us, but inevitably, given the hundreds of thousands of passengers who travel with us daily, some people will regrettably be disappointed by aspects of the timetable change.
We do realise this information will be largely disappointing, but we hope it can at least be of some use. Thank you once more for bringing your concerns to our attention.