This paper makes an interesting case for 100% stock indexes, regardless of age:
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4590406
It basically takes a large number of past yearly market performances, randomizes them into lifetime-sized market performances and then runs a simulation with different asset allocations over it. The results go against the usual advice: "An optimal lifetime allocation of 33% domestic stocks, 67% international stocks, 0% bonds, and 0% bills vastly outperforms age-based, stock-bond strategies in building wealth, supporting retirement consumption, preserving capital, and generating bequests."
It doesn't get more simple than that; just DCA into FTSE All-World or MSCI ACWI and stay the course. Ignore bonds, bills, BTC, gold and everything else. As for risk-intolerance, that is on the individual. If you feel you have to sell, regarless of the statistical evidence, it's on you, you are timing the market and that will likely be a bad thing.