I agree with you that the 2 minute silence should be for this occasion, and this occasion only. I think as a nation, we could take two minutes out of however minutes there are in a year to show our respect and gratitude.
...and many of us do take the time to take part in services and ceremonies on Remembrance Sunday, as has been our tradition as far back as I can remember (to the 1960s, so a while).
Exactly. Virtually no-one alive today knows anyone who was around in WW1.
Eh ? How do you work that out ? 
All my Grandparents, and most of my Great Aunts and Uncles were around in WW1. Of course, I don't remember those who died - the brothers, the husbands, the fathers, but I remember many, many people who were teens and young adults at the time. I know many, many folk who are up to 40 years older than me, and all of them will remember even more people. Even my dc can remember some people who were alive in WW1 (far fewer of course, but there are some).
You need to check your maths.
All that said, in my silence, I think of all the war widows / widowers and the children and parents of our armed forces who have died in more recent conflicts, not just those who died in WW1, and those injured in those conflicts, both physically and those with PTSD.