=SUM(COUNTIF(INDIRECT({"Sheet1","Sheet2","Sheet3"} &"!A:A"),"yes"))
or
=SUM(COUNTIF(INDIRECT( "Sheet" &{1,2,3} &"!A:A"),"yes"))
counts the cells in 3 sheets that have yes in column A as an example.
This is not an array formula. (it doesn't need to be array entered). That
may not be true for any formula of this type that you come up with, so if
you don't get expected results, try entering it as an Array formula.