What you're describing is just like their original system. The problem is that so many people these days don't quite know what a URL is or understand how important it is to be at the correct one. As a result, people were putting the URL into search engines, and choosing a match that "sounded good" or accepting suggestions and they ended up at scam sites. (Some scam sites were actually buying google ads to be shown at the top of searches.)
In one case, a guy let scammers root around in his computer, install bogus security software, and he got charged $800 for that – all starting from trying to link his Roku. People used to blame Roku for making such a scammable system all the time.
So, Roku came up with this system that currently is more fragile, but has dramatically reduced the complaints about getting scammed.
Anyway, that's the why – I know that doesn't help with the frustration when it doesn't work though! You've probably viewed the big thread where some people got past it by either rebooting the Roku or rebooting the router. (If not, maybe try those.)
