There are a HUGE number of people out there who would follow stricter rules. I am part of groups who think restrictions should be in place now and have lots of friends and family who mostly stay indoors and even some who have isolated throughout, apart from a few walks. However I fully agree, the majority of people will not comply. Govt have royally stuffed this up. I suspect this is in part why they haven't reintroduced measures, because they've spent so long telling people this is it, to go back on that would be a huge step back.
This is falling apart though. NHS is near at capacity. Hospital beds are low, staff are broken and call handlers don't have capacity to deal with everything. In the last month I have been to out of ours and experienced a dr during a consultation who told me they felt dizzy and walked out, as well as being on hold to 999 for an ambulance. I live in an area that has never been effected throughout the whole pandemic by the NHS being stretched. I'm a Childminder and I see across the board how families are struggling. A few weeks ago I had to close as my child had a continuous cough and when the parents picked their children up, although understanding one of them had to take their child into work with them because they are a keyworker and the other people who were normally there were also off due to covid/childcare issues. The thing is, we're all testing (as i feel we should be) but we're all now mixing, so all bugs are rife. I don't think our govt understand the extent of normal bugs and how many tests will be needed and how much this will take people out of the workplace. I think lower level measures would curb some of this. But they won't do it, they'll wait until it gets past really really bad and more needs to be done.