Look again at the formula =TODAY()>=I2

It states that todays date is bigger or equal to the date in the cell I2. Now, if the cell is empty, how does that affect the formula?

If you select an empty cell, format it as date and write in the number 0 (zero) this is what you get 00.01.1900 so if the cell is empty, Excel probably treats it as 00.00.1900 or something like that, meaning that todays date will always be bigger than the default date value, and the rule of Conditional formatting will apply.

Solution? Only apply the rule to cells and areas with actual values by using Format painter.