They can’t communicate with humans, and their thought patterns are likely very different to ours. But I wouldn’t be surprised if they are just as complex. Whales and dolphins especially.
How complex are a humans thoughts if not raised by other humans? How much of complex thought is transferred generationally through example and language. An octopus biology may be capable of extremely complex thought, but as a species they are limited by their inability to document and propagate information in written form, unless they have some kind of telekinesis and can beam and download memories from each other.
I'm not a big believer of thought complex thought patterns that fail to manifest in any meaningful way. If they are as sentient, they should have to make a difference.
The same attitude was shown by humans towards other humans a thousand years ago. If they couldn't understand the language of another tribe, they considered that tribe inferior and called them names signifying that.
The ancient Greeks called non-Greek-speaking peoples "barbarians", suggesting they are uncivilised, primitive. To this day, the name of Germany in Polish means "those-who-cannot-speak".
One of our major advantages against other animals are versatile hands with opposable thumbs.
I wonder what corvids could do if they had hands and not just beaks. They are fairly smart, I would expect them at least to build some more complex structures. Which would trigger a self-reinforcing cycle between improving tools and improving brains.
Now it dawns on me that it might be possible in the future to give them the necessary genes to grow hands ... wild.
To you. If someone doesn't speak to you and doesn't respond "meaningfully" to your input, does that mean they do not have complex thought patterns? With that philosophy, it's probably for the best that you don't take care of sick people :)