You are comparing the risk of a young person dying of Covid over one year with a person dying from a lifetime of driving or whatever. It would be more honest to assume that everyone will eventually get Covid, and then compare the risk with walking.
On top of that you are forgetting that we don't know the extent or severity of "long Covid" in young people, or that even if people don't eventually die, the sickness can be very severe with long term implications, and that while they are sick they are occupying hospital beds that are no longer avaiable for other patients with cancer or whatever
For the rest, it's simply unworkable as well as inhumane to isolate everyone over 65. There will always be "leaks" - who is going to care for these people? Are they never to see their families again? I realise that you are under this age, so those considerations are of no importance to you, but maybe Alan would not be happy to be sent to some latter day leper colony.
Perhaps I was being a little deliberately loose with what I was choosing to reference. However my point stands, C-19 is much less risky then other occurrences we rarely ever think about, such as strolling along the sidewalk. Who would have thought being a pedestrian came with a 1/610 chance of dying. That is a 0.16% chance of dying on the side of the road, yet we still take those strolls.
Meanwhile, the IFR for under 45 is 0.05%. Note, although my previous comparison may have been a little tongue in cheek, comparing these two stats is statistically sound. So, 0.16% chance of death and we doing nothing about it, vs. 0.05% and we are suppose to shut down the world. BTW this does not take into account the chances of catching it first, which if we did, would lower the chances of death from C-19 even more over a lifetime.
PS
Your second point is well intentioned, but what are your solutions, just hole up for all of time.
And your third point in contradictory in a few ways. Just to elaborate on one of them, in essence you are arguing it is inhumane to lockdown seniors, not to mention even if we did some of those pesky bastards would slip out anyway. So, lets just lockdown all of society instead, much more humane.
BTW, I am not for locking down anyone, even seniors. I am for letting people make their own risk assessment, and for those who are in the vulnerable category, provide concessions that will allow them to stay locked up if they so choose to.