Hospital capacity is the main reason why we can't just allow everyone to do what they want until every group has received the vaccine. The reason why is whilst the younger (age <50) population generally won't die many are still hospitalised.
It's a fact that the majority of people admitted to hospital are not in the most vulnerable groups, they'll survive but they'll still need care. Many of these people won't receive the vaccination until the summer.
If we can vaccinate the whole population by autumn then indeed we can then do whatever we want but that requires a very high vaccination rate, one which we are miles off yet.
There's a calculator below which estimates when you'll get it based upon a more likely average vaccination rate. At 32 the earliest I'll get it is July running possibly into October where I wouldn't get the second dose until near Xmas.
The vaccine queue calculator for the UK estimates where you are in the queue to get your COVID vaccine based on your age, health, and job.
www.omnicalculator.com
If the government can get rates upto 2 million as claimed then indeed we'll be back to normal by late summer.