The general opinion of GDS is that they live in a bubble of newness, without much reference to the real world.
Whilst the digital only channel approach is a good aspiration, the previous 1990's strategy from the Major and Blair governments was to maximise the channel availability. To allow the citizen the choice of how they communicate with government and maximise inclusion.
Digital only does not do that, in theory, it means less civil servants, and less cost, easy and quick service for the taxpayer. As always politicians forget that we are virtually all tax payers, and those who are not, are on low incomes and benefits or pensions. There may well be a good many silver surfers out there, but not in sufficient numbers to make a difference, and even those with access to IT kit, do not always have the confidence to negotiate forms.
The idea is right, it's just 30 years too soon, and there will always be people who can't access IT.
Psychologically, if you have a problem, talking face to face with another human being is the way to solve it. You can't communicate with a form, and a lot of people will give up if they don't understand the process. GDS do not understand this, any more than they understand the demographics of the citizen. The government serves the citizen, not the taxpayer. Somewhere are politicians seem to have forgotten what universal suffrage means, and who they work for.