1) There are maps where Katie's skill won't be usable in time for the early rush and most players do not have the platinum soldiers. Even if they have the plats, no reason you can't use a cheap UP ramp for extra points in certain maps. Also, you really ought to stop saying stuff like "newbie silver users" and "dummies can ditto their map on" because it really makes you come across as a whale that looks down on non-whales. The fact there are some players who have played since launch and still occasionally use silver units means silvers are not newbie-exclusive units.
2) Using her for what she's meant to be used for is a nasty use?
3) Why would you bring up a black unit to compare to a silver unit? Blacks are designed to be OP (though some aren't used as often, like Berna)
4) The point of the posts is Claire is comparable to platinum units of the same class, while being more likely to show up in Shrine due to lower rarity. In other words, she's not useless even if you have been playing a while (unless all your plat archers are AW already, then maybe not)