At what point do you own too many stocks / is the fund holding too many positions?

I know ACWI is popular, but when I look at the sheer number of stocks and the percentage they have in the portfolio I wonder if it's the most efficient way to capture global exposure.

2.2k companies, the median holding size is 0.01% of the assets... a company that size would need to grow 100x to give you a 1% return... with the trading fees involved I wonder if it's worth going to this level of broadness?

If the company performs that great to have material impact on performance then it would come into scope of a fund with a much smaller number of stocks (e.g. 500-1000). This might be something that's been answered already.