Good discussion. I agree that at record low interest rates, a mortgage is not a big expense. That assumes, of course, that you bought a reasonable home for a reasonable price. Unfortunately many people use lower interest rates as an excuse to buy a bigger, nicer house and still have monthly payments that don’t allow them to save money.
I believe that your personal house is a liability rather than an asset, so it is a cost to minimize. For some that means renting, for others paying cash. Paying cash will ensure you buy a house you can afford!
But if you bought a home that you can afford to pay off using a cheap loan, investing the balance will work well. As long as you have enough financial education to get a rate of return higher than your mortgage rate, you will be money ahead. Then, in a decade or two when you want to retire, take the excess money you have from your investments and pay off the balance so you are debt free in retirement.