Most other carts on the market work as a software package that you would install and configure on your own server, so that software can control the entire purchase and payment process from start to finish entirely on your own server. If an outside service is involved for payment, in that case it's usually entirely in the background and invisible to the buyer.
As E-junkie is a centrally-managed, independently-hosted cart system shared in common among all our merchant subscribers, and which hands-off the checkout stage of purchasing to a third-party payment processor's Web site, we take care of the server and software end of things for you, and the payment processor takes care of the payment end, so this spares you the considerable technical hassle of installing, configuring and maintaining that software (along with an SSL certificate for your own domain, etc.), but some inherent technical limitations are part of that tradeoff.
We are indeed an entry-level system, very simple and basic for very simple and basic needs, and that is intentional and by design. You can try to trick out a VW Beetle to be more like a Lexus or Jeep, but what you wind up with will never be as good as just getting that Lexus or Jeep in the first place, if that's what would actually meet your needs. Perhaps you have simply outgrown what we are and what we can do for you.