For example, when you write "inconceivable," you're not regurgitating every single letter in a line from memory. You probably remember the prefix "in," "conceive," and you know "able." You probably also know the common patterns "cei" or "eive" or "con," so the word "inconceivable" really isn't as complex as the initial length makes it look, as long as you know the blocks.
Kanji/hanzi are the same way -- they look complex and inscrutable to the uneducated eye, but they're all made of common building blocks that make it easier to remember them. After all, human memory works roughly the same way all the world around; people wouldn't be able to memorize thousands of 20-stroke character if they were all completely patternless.
The vocabulary utilizing kanji/hanzi works the same way.
Someone could look at "inconceivable" and say "well shit, that doesn't make sense! It's long, you'd have to memorize so many letters, and the letters themselves have so many bits! Plus it has 'in' in it, which makes no sense because 'in' commonly means 'inside of something', and 'con' usually means 'to swindle someone'! This alphabet thing is completely useless."
It's absurd, reductionist, and a bit offensive.