you can also very easily write a computer program to solve a maze, but most of us would be reluctant to attribute "thinking" or "intelligence" to the program, or the computer running it (except in a very casual sense of the word - like, the computer's taking a while to do something, we might say "it's thinking", but it's not really thinking).

in the case of computers, we're applying our own psychological concepts to phenomena where they're only appropriate at an extrinsic, 3rd-person point of view - from the outside, what the machine is doing looks like what the intelligent organism does - while what's actually happening in the system is absolutely unlike the psychological phenomena on which those concepts are based.

by a classic analogy: just as a computer simulating a hurricane isn't windy or wet, a computer simulating a mind isn't thoughtful or intelligent.

i think the same applies to plants, slime molds, etc - they aren't simulating, that implies some kind of intention, but what they're doing only appears like intelligence because it happens to resemble the behaviors that we associate with actual thought.