If there's design, there's a designer. Who's the designer?
In your own words: It isn't science unless you posit some attributes for the Designer, such as means, motives, location, times, places. When and where did the Designer intervene in evolution?
Then what you call science isn't really science unless you can tell us about the source of the designer.
Living things are designed by the same nature that builds snowflakes. If you choose to believe God set it up this way I have no problem with that belief.
But the history of the building of the living snowflake is as described by science, regardless of the ultimate cause.