A week or so ago this message appeared on the Portfolio page, I assume the Flash Player requirement will be gone soon: > Google Finance is under renovation. As a part of this process, the Portfolios feature won't be available after mid-November 2017. To keep a copy, download your portfolio.
IMHO if they can't change things without removing functionality, they should just leave well enough alone. They don't have to "support" the old version or do anything special with it; just leave it alone in its current, working, state.