The market(as measured by the S&P) is up ~55% since the 2016 election.
Based on that piece of data, it's fair to say that:
1) 50% return over that time period was a realistic result for someone ~90% or more in US equity.
2) Larger returns (70% or 90%) are only realistic over that time period if:
A) someone had a portfolio that was non-diversified or overweighted certain sectors that did well during this time period (i.e. Big Tech - the Nasdaq outperformed the S&P by quite a bit), or
B) they employed leverage
Either of the above means that individual took on more than market risk to get those higher returns. 70%+ returns over that time period aren't impossible, but those that got them are the exception rather than the rule, and they didn't get there without substantial risk exposure.
If I look at my personal ROI over that same time period, it was in the neighborhood of ~40%. I'm mostly equity, but I have more international exposure than the average investor, and that part of my portfolio has fared relatively poorly relative to the U.S. markets over the past couple years. My *net worth* increased by closer to 70% over that period, but that's because of contributions, not market gains.