When you use Webflow's wildcard pattern, it's somewhat context-aware. If you use it after an =, for example, it will only match the value in a querystring key-value construction.
e.g. /old-page?id=(.*)&name=(.*) -> /new-page/%2?id=%1
If you use it right after the querystring separator ?, it will match the entire querystring.
e.g. /old-page?(.*) -> /new-page?%1
e.g. /old-page?(.*) -> https://new-site/new-page?%1
Webflow doesn't allow you to redirect pages that already exist, unless you include a querystring.
For example, this won't be accepted into the redirect table;
e.g. / -> https://new-site.com
But this will. The difference is the query string.
e.g. /?(.*) -> https://new-site.com?%1
If you want to redirect the homepage without a querystring, you cannot accomplish this with Webflow's redirects feature.
You can instead do this using a META tag in the page HEAD.
<meta http-equiv="refresh" content="0; url='https://new-site.com'" />
