I don't think it is the government's plan for people to get this slowly. The plan currently across Europe appears to be to keep R0 below 1 and to get numbers of infections low enough for contact tracing to be effective. This is not herd immunity. This is massive suppression.
When governments talk about "easing" the lockdown, what they are talking about is using up the slack in R0. If R0 is currently 0.7, then there is up to a 0.3 amount of slack. Easing in this case will be a small measure, not total lifting. I would imagine, as an example, permitting some additional shops to open and opening up schools to year 10 and 12 may use up all of that additional R0.
If R0 goes above 1, then we will be in a far worse state than we are now. R0 above 1 will result in exponential growth. This may well be slower than we saw before, where cases were multiplying by 10 every 10 days. However, even if the x10 time were 1 month (so three times slower than when we were just washing hands), this is what would happen to the figures:
May - let's say 100 deaths per day
June - 1000
July - 10,000
August 100,000
As you can see, even slower exponential growth is not something we can contemplate.
Because figures have never grown so high, they seem unrealistic. But this is how exponential growth works. Remember when we only had 1 known case in the country? It didn't seem like we would get here. But the gap between then and what we got to now was only a couple of months. A couple of months from here is hundreds of thousands dead.
We will not be getting anywhere close to back to normal until we have a vaccine and people just need to get used to that, hard as it may be. The choice is between some form of stringent social distancing or hundreds of thousands dying per day. There is only so far we can ease before we flip to the position of having an unconscionable amount of deaths.