UAC has never been a security feature. Microsoft has NEVER claimed that UAC was a security feature. It's a convenience feature that acts as a forcing function to convince software developers to get their act together.
And if you don't like the default settings, you can make a trivial change to increase your prompting level back to where it was in Vista and all these "exploits" go away.
The ONLY secure scenario is to run as a standard user (with no admin privileges) and use fast user switching to switch to an admin account when you need to make configuration changes to the machine. But most users won't put up with that level of security.
Heck, look at how much people complained about the UAC prompts. Imagine how annoyed they'd be if MSFT forced them to log into another account to change their system configuration.
If UAC is not a security feature, you need to let the people writing about it on Technet know (because, last time I checked, Technet was the definitive source for technical information about Windows):
User Account Control (UAC) is a new security component in Windows Vista. UAC enables users to perform common tasks as non-administrators, called standard users in Windows Vista, and as administrators without having
to switch users, log off, or use Run As. A standard user account is synonymous with a user account in Windows XP. User accounts that are members of the local Administrators group will run most applications as a standard user. By separating user and administrator
functions while enabling productivity, UAC is an important enhancement for Windows Vista.
To help prevent malicious software from silently installing and causing computer-wide infection, Microsoft developed the UAC feature. Unlike previous versions of Windows, when an administrator logs on to a computer running Windows Vista, the user’s
full administrator access token is split into two access tokens: a full administrator access token and a standard user access token. During the logon process, authorization and access control components that identify an administrator are removed, resulting
in a standard user access token. The standard user access token is then used to start the desktop, the Explorer.exe process. Because all applications inherit their access control data from the initial launch of the desktop, they all run as a standard user