I agree with you. Unless there was a notice on the outside of the box specifying minimum upload speeds, you should return the product to the retailer for a refund.
This is similar to an issue that arose in the mid-90s with computer games. Players were buying games, taking them home and finding that their PC was not powerful enough. They would return to the store, and be told that since they had opened the box they couldn't get a refund - they may have just copied the game to another CD. End result? Computer games sold in Australia have on the outside of the packaging both the 'minimum' spec and a 'recommended' spec.
What you have bought is not 'fit for purpose', and if that was unclear from the packaging then you are entitled to a refund. The fact is that it was sold as a consumer device, and as an effective 'plug and play' security solution. (Yes, I know that Universal Plug and Play is horridly insecure.)
Seriously, 'Windoze'? Please don't let this descend into one of those 'Crapple' vs. 'Windoze' vs. whatever flavour of Linux or BSD people happen to be in love with today.