Nike I don't think your realise how important it is that people who are older or have chronic illness or disability are able to maintain whatever exercise they can do. It can have a dire effect, fast, if they don't, and can be much more difficult if not impossible to come back from than for another person.
If people are young, fit, healthy and unworried by the virus then they can go somewhere else much more easily, anyway in fact, and they would suffer less from being unable to exercise anyway. You can't put their need to be outside or exercise above that of the 'vulnerable' just because you feel the need to punish the vulnerable for the sacrifices you believe have been made for them.
I strongly believe that it is not as simple as sacrifices being made to protect those most vulnerable to covid. You must be quite idealistic to think politicians would go so far to protect that group! You need to think through what would have happened if the virus had been allowed to spread completley unchecked. Even if severe illness and death among a more vulnerable cohort had not been considered the impact on workplace attendance, customer behaviour, international response, keyworker provision, education, economic activity etc would have been immense, not to mention soaring death and disability from non covid causes.
In addition many 'vulnerable' people can't just stay away to protect the NHS, many of them are the NHS. Remove obese, the over 50s and people with other underlying conditions you would have almost no consultants, a third less GPs, few nurses and support staff. Then remove all those who share a home with someone vulnerable. Repeat for teachers, other keyworkers and the private sector. Many not particularly vulnerable to covid would then be rightly scared to participate in society with help and safety nets so compromised. Never mind all the people you might see as young and fit but who fear being the unlucky minority who become severely ill, or who fear long covid or other unknown long term consequences. Never mind the increasing risk of mutation as cases rise, which may set us back years and change the nature of the vulnerable.