I think the main benefit is that you are not forced to use any other library or framework like React or Vue on top of it. You can simply use HTML or Web Components. However, Astro can perform similar tasks to Next or Nuxt, such as SSR, ISR, static site generation, and middleware.
Another differences and benefit of Astro is the island architecture, compared to other frameworks. This means you can implement micro frontends.
Island architecture and micro frontends are features that companies or projects may want if they have multiple teams. For example, one team could be working on the checkout process, another on the shopping basket, and another on product listings.
Now, you can use Astro to combine these components on a single route or page. And you control how this components are rendered. Astro also allows you to share global state between these islands.
This approach is beneficial because teams can develop and ship a single feature while having full responsibility for it. However, it also has downsides, and similar outcomes can be achieved with non-island architectures.
For instance, if all teams use React, it is common for each team to use a different version of React, forcing the browser to load all these versions. The same issue arises if one team uses Vue, another uses Angular, and another uses React or any other framework.
I'am not fully convinced that it will change the web. It is basically a Next or Nuxt without the library/framework login. And it overs the Island-Architecture, that is usually only beneficial for very huge projects.
But, you should try it. I work with Astro since there first release, now for several years, and I can recommend you to give it a try.
It is also a nice tool, if you want to get ride of React or Vue and move to web-components or if you want to replace Next or Nuxt. You can do this with Astro, step by step.
Another differences and benefit of Astro is the island architecture, compared to other frameworks. This means you can implement micro frontends. Island architecture and micro frontends are features that companies or projects may want if they have multiple teams. For example, one team could be working on the checkout process, another on the shopping basket, and another on product listings.
Now, you can use Astro to combine these components on a single route or page. And you control how this components are rendered. Astro also allows you to share global state between these islands.
This approach is beneficial because teams can develop and ship a single feature while having full responsibility for it. However, it also has downsides, and similar outcomes can be achieved with non-island architectures.
For instance, if all teams use React, it is common for each team to use a different version of React, forcing the browser to load all these versions. The same issue arises if one team uses Vue, another uses Angular, and another uses React or any other framework.
I'am not fully convinced that it will change the web. It is basically a Next or Nuxt without the library/framework login. And it overs the Island-Architecture, that is usually only beneficial for very huge projects.
But, you should try it. I work with Astro since there first release, now for several years, and I can recommend you to give it a try.
It is also a nice tool, if you want to get ride of React or Vue and move to web-components or if you want to replace Next or Nuxt. You can do this with Astro, step by step.