Compared to 'Us' or even 'Get Out', the ending of 'Nope' and the themes and motifs it presents is actually pretty straightforward and barely even subtext.
Let's start with the fact that the UFO looks exactly like a big, giant eye floating around the valley between Jupiter's Claim and the Haywood Ranch. As the Haywoods realise, whatever looks directly at it gets sucked into it without any discrimination. The UFO - Jean Jacket - is basically us, the audience. The way in which we consume content nowadays is practically alien. Think about how many articles there are about the ending of 'Nope' alone, never mind this one you're reading now. How many videos on YouTube, TikTok, wherever - that's just on one scene, mind. And we're all just hoovering it up like Jean Jacket.
The whole meaning of 'Nope' is that we, the audience, are taking in new wonders and spectacles every day, but nothing really sticks inside and we place no value on it because it's effectively become commonplace. It's like Michael Wincott's character, Antlers Holst says. (whose name sounds weirdly like Hoyte van Hotema, the actual cinematographer on this movie) After they get the shot on their non-electric cameras, he gets up and walks away in disgust, saying, "...we don't deserve the impossible." Yet, in the very next scene, he then grabs his camera and goes right after Jean Jacket and consequently gets sucked by it. Even "artists" like Holst are guilty of trying to please and capture the audience's attention, even if it destroys them.
Throughout the press tour for 'Nope', Jordan Peele repeatedly talked about how he wrote 'Nope' at a time when he feared for the future of cinema and wanted to make something that showcased cinema in all of its scale. But as he went further in, he realised that trying to chase the addiction of attention presents a far darker, disturbing proposition.
Put it simply, the ending is - we think - Jordan Peele talking about the eventual collapse of content as we know it. This probably explains why some people walked out of 'Nope' a little - pardon the pun - deflated. Even though Emerald and OJ got "the Oprah shot", even though they survived, the ending feels curiously empty. As the TV crews advance on them, Emerald looks past them to see OJ on horseback. In the end, the chase or the hunt for attention doesn't matter to her anymore. All that matters is the human connection she has with her brother, not the attention she's been chasing throughout the movie.
Let's look at what actually happens. After Jean Jacket turns into its evolved form, Emerald comes up with the quick-fire idea of letting it eat the huge inflatable from Jupiter's Claim. All of Jupiter's Claim is built on mass-market, cookie-cutter bullshit that has no basis in truth and is made with the express intent of raking in money with no artistic value or merit. So if Jean Jacket is a stand-in for our addiction to consuming content and Jupiter's Claim is that, then what happens?
Eventually, the whole thing will collapse in on itself because one is as empty as the other. It's all made up of hot air and will just burst in on itself, taking both out with it.