This is general work advice not just interview advice

bad: I disagree with the way this is done/this is just bad. Lets do X!

good: I see the motivation with the current approach and understand the goals but i wonder if we might be better served by doing X instead. Usually this allows for Y benefits, but I'm open to discussion here.

Add some fluff to ensure nobody gets defensive and articulate your flexibility (even if you don't really have it)