So he starts by saying he isn't going to be guided by dates but by data, but then goes and gives dates anyway. Seems somewhat counter productive to me.
I can understand the need for some kind of goal, both for people's sanity but also as a point at which people can question to government on "you said by now we could do X". But giving exact dates seems a bit silly considering how quickly so much of this changes, and how many times over the last year the government have had to backtrack on dates already announced.
However, in general the dates announced, whilst potentially a little too far out for some of the smaller things, seem somewhat sensible to me. Especially if we do want this to be a irrepressible removal of restrictions (otherwise we'd just end up having to pull the breaks right away if we start too quickly). Better to plan to be cautious and if things continue to go well (especially around vaccinations etc) then there's the potential to pull forward some of the dates.
Though some of the specifics for each date seem a bit odd, especially if you compare with some of the other things allowed - take after May 17th, I can go to a football stadium but not meet in a group of 3 people in a pub where those 3 people come from different households? Doesn't really make sense!
There are two issues here - most obviously vaccination, plus natural peaks and troughs.
You are forgetting the lockdown.