But they can make plans, they have goal-oriented behavior that drives them to seek out a goal that exists beyond their senses. If I leave the house through the front door without giving my dog his customary distraction, he goes out the back door and around the side because he knows that, if I haven't properly secured the fence, he can get out through the fence to reach me. Nothing about that involves his senses, it's just something he's figured out.
Now, I doubt any part of that involves an internal monologue because they don't use language (even though they can, in fact, understand limited language). If they don't use it themselves, they probably don't figure things out in their heads that way, it simply wouldn't be very efficient. But they certainly possess more complex internal cognition than just "I smell food" or whatever.
To be honest, that's me too! (And I also might be autistic.) But I'm capable of thinking things out verbally, something I do particularly in regard to programming and architecture problems, or figuring out what to say to someone else. So it's a tool that's available to me. I don't think it's available to my dog, but I'll bet he's doing virtual paws.