Are US companies, including Delaware LLCs, used as shells for dubious purposes? Yes. That the US is one of the better places to set up a shell company is a not-so-secret secret.

But it's not clear what use case you have in mind, and I think your comment deserves some qualification:

1. Even if disclosure of your name and personal details isn't required to set up a Delaware LLC, almost everyone is going to be identified anyway: through the registered agent, the EIN you obtain from the IRS, your bank. Sure, if you have a team of lawyers and layers of layers of shell companies across multiple jurisdictions, it's trivially easy to keep your ownership pretty effectively hidden but the minute you have any assets in or moving through the US, it's trivially easy for the authorities to figure out who you are once they have a reason to.

2. The legal "advantages" of Delaware basically aren't relevant to single-member/closely-held companies because you're not going to have any disputes with yourself over the corporate structure. If your Delaware entity is doing business in other states, you are exposed to the laws of those states as far as your business operations are concerned.

Delaware law is not so much favorable as it is well-trodden. Of all places here we should understand the value of the network effect.

Which is why they're all registered there. And the state of Delaware gets a fortune as a result from all the activity it creates.

What do you mean “shell companies”? Most Delaware corporations don’t hide their identities.

And yes, the legal process is advantageous in DE because the courts have a massive body of prior law. Decisions are made quickly. It doesn’t mean the courts routinely rule for corporations.