I guess a couple things come to mind.

You mention that paying off the mortgage 5 years earlier is piece of mind and more flexibility once the mortgage is paid is flawed logic in my opinion. You are just moving the debt from a mortgage to a HELOC. If/when you sell your house, the proceeds from selling the house will have to pay off the HELOC. This might not actually be the desired use of the proceeds from selling your house.

(reinvested) dividends make up a large portion of total return. It seems like you are still "reinvesting" the dividends, except you will be paying off the mortgage first and then drawing on the HELOC. It shouldn't matter either way. But you are correct that only focusing on dividend paying stocks eliminates a massive amount of potential growth companies that have much higher upside. Whether you get a dividend, or sell the stock to pay off your mortgage the result is the same. However, you could see some tax efficiencies by realizing capital gains rather than dividend income.