Opponents might expect blue to focus solely on control, but by integrating ramps, you catch them off guard and diversify your strategic options
Not only can we exile lands we put into our graveyard but some of the most popular white staples: Esper Sentinel, Spirited Companion, Knight of the White Orchid, or Archaeomancers Map
Thats just one combo off the top of my head, and there are many more here
Moreover, the grixis uncommon Planeswalkers tend to be better than green-whites, making Proliferate even easier to set up for them
If you manage to combine your Montunui Island Paradise Location with Reckless Questers like Maui Soaring Demigod, you can ramp your Inkwell, but there are few top-end threats to capitalize with