Sivir's Damage

sivir can wipe your base out faster than any other adc I can think of

She deals good damage, but she's no jinx/draven/lucian. With the proper items and using your W as an AA reset you can still burst targets down pretty quickly. Also with her W and Q she does a lot of AOE damage. Her strongest point is the ultimate and the survivability with the spell shield. If you ignore sivir she'll still destroy you like every other well played ADC.

then why is she considered a god tier adc?

She does, she just needs items, the main reason she is played is for her long-range poke (Q), wave clear (W) and spell shield (E), ohh and that great team-fighting ultimate (R).

And did I mention the fact her passive is a built-in furor?