When you say "I see" sarcastically, it suggests you comprehend or are looking into flashbacks or suspicious of something. but if you say "i see it" it means you can see physically.
When you say I see you often “see” (understand) what someone is saying. Now there are more than one way to see or fail to see the world. The world is a complex, constant changing plane where “seeing” is irrelevant. One day you will “see” something, the next you will be blind.
