I will not argue about someone's ability to buy a new house in the current environment. But in this thread discussion is focused on existing homeowners moving to a new house.
In your case (assuming $300K original house price) you will sell it for $600K, net $264K profits after commissions. Use profits plus $60K of original downpayment and any additional equity in the old house as a downpayment for a similar house at $600K. The new mortgage will be similar to one you had in 2007. Same rate and most likely smaller principal. Not a big difference.
All true (except multiply all those dollar figures by a factor of 4).
The problem is that I'd be taking on a new 30-year mortgage while being about 10 years away from retirement rather than ~26 years away from retirement, which has certain implications on my ability to afford that mortgage over its full term.
When you are retired you don't need to live at the same place. World is your oyster. The capital gains from your house ($1.2M already, more in 10 years) will allow you to pick new house almost anywhere without worrying about mortgagees. You won't care about schools or extra bedrooms for kids, for instance.
Statistically very few people stay at the same house for 30+ years, most move within eight.
We bought in 2007. Our house more than doubled in price since then. I’m not sure I could afford to buy it now if I was a typical 20% down buyer.