The US government was
deliberately not set up to be a direct democracy. Those writing the Constitution looked at the historical examples before their time, and concluded that direct democracy was too prone to degenerate into mob rule. So they didn't do that - they set up a republic instead of a democracy.
Yes, you could replace the US House and Senate with a web site, at least in theory. In doing so, though, you are changing the form of our government. You'd better think hard before you decide that you know better.
And, if you conclude that your idea is still a good one, then to actually implement it, you have to amend the Constitution. Unless you have a plan for doing that, the answer to the "can" question is "technically yes, politically no".
(In fairness to the idea, though, Congress has been showing a clear trend toward increasing dysfunction and uselessness for the past few decades...)