I think the biggest issue with Deno is that it fixes real issues but in the wrong way.

Take the sandboxing stuff. In theory, you have always been able to sandbox your applications. There are so many tools that let you limit what domains an application can access or restrict access to the file system. This doesn't need to be handled at the language/runtime level. It's just that people were lazy before, and they will continue to be lazy afterwards by running Deno applications with fewer than the minimum set of restrictions because that's easier.

The more complete way of solving the problem would have been capabilities. Rather than sandboxing the whole application, you instead sandbox each individual function. By default a function can make no requests, access no files, execute nothing, etc. But while the application is running, you can pass individual functions a token that grants them limited access to the filesystem, say. This means that trusted code is free to do what is necessary, but untrusted code can be very severely limited. It also significantly reduces what dependencies can do: if you're using something like `lodash` which provides random utilities for iterating over object keys and the like, and suddenly it starts asking for access to the web, then clearly something is wrong, and the runtime can essentially make that impossible.

It's also great for things like build scripts, which are a common attack vector right now. If your runtime enforces that the build script only has access to the files in the project folder, and can't access arbitrary files or run arbitrary commands, then you're in a much safer position than if your build script can do basically anything.

This concept has been explored before, but JavaScript is basically ready-made for it. The language already has everything you need — a runtime that also acts as a sandbox, unforgeable tokens (e.g. `Symbol` or `#private` variables), etc — and you can design an API that makes it easy to use capabilities in a way that enforces the principle of least privilege. The biggest problem is that there's basically no way to make it backwards compatible with almost anything that works with Node, because you'd need to design all the APIs from scratch. But one of the great things about Deno at the start was that they did try and build all of the APIs from scratch, and think about new ways of doing things.