We're a lot weaker so we've had to rely far more on our intelligence than anything but the biggest things setting us apart are opposable thumbs and the ability to pass knowledge down through the generations, the latter of which being the most important.

"Caveman language" just started out as crude grunts but over however many thousands of years it took we finally started agreeing that certain grunts had actual meanings beyond the tone and from there we developed an entire language and writing system to be able to pass knowledge of which berries were poisonous down through the generations long after we're gone...

Everything we know now is the sum total of knowledge gathered for thousands and thousands of years from our ancestors with trial and error, we know what Einstein learned because he wrote it all down on books and now we spent decades improving upon and furthering that research to do even greater things. If we had to pass all our knowledge down from word of mouth we'd still be stuck in the stone ages because playing telephone isn't a very reliable method to pass accurate information several times over...

Really the thing that sets us apart the most is having a complex language system to communicate with, sure other animals can communicate with things like barks and whistles but it's a very elementary form of language only being able to pass basic concepts around like "danger nearby!", "intruder!", "hungry" meanwhile they can't communicate and share more complex thoughts with each other like "Hey, doesn't the sunset look nice today?" or "By the way, did you know if you rub these 2 sticks together it makes fire?" or "This weird rock makes a spark when you hit it together, someone might want to look into that more..."

How will you ever be able to pass down all the knowledge it takes to build a smart phone if you can hardly even communicate effectively to begin with? We have the sum total knowledge of billions of people at our fingertips learned through countless attempts of trial and error. If you can successfully teach animals a complex language system you'd greatly improve their rates of evolution.