We actually have a huge initiative at Clerk with what we're calling "Elements" which gives a you "radix-like" way to build up the UIs, for significantly easier customization - especially when you're trying to go completely custom. The default modals will always be easier to use, and we're simultaneously working on getting better customization there.

Here's an example building a "Sign up" modal in the shadcn style.

https://clerk.com/docs/elements/examples/shadcn-ui

We've only tackled a few of the UIs, but UserProfile, OrgProfile, etc. are coming soon.