"Real" ringworlds

[dogscoff]

you cannot make something more complex and expect it to get intelligent.

We're not doing that- not every complex system is "expected" to gain intelligence. For example no-one is expecting the global telephone network to suddenly achieve sentience. (although that would make a cool scifi book=-)

However, it is scientifically provable that at least one very specific kind of complex structure (the brain) gives rise to (or is required to harbour) intelligence.

Your argument seems to be equivalent to "this bit of unrefined metal can't open a tin, therefore tin openers do not exist."