At the end of 2019 a 60/40 portfolio may have been judged as too conservative. But true to form, a 60/40 portfolio is almost back to even as of the end of May 2020. Even if the S&P 500 is 200 points behind the start of the year, a simple rebalance at the end of March would have a 60/40 balanced portfolio down less than 1% ending May 2020. Many of the new math alternatives are struggling to improve the 60/40 portfolio, net of fees.
Asset Allocation between stocks and bonds is still the most important decision in controlling risk and reward over the long term.