We can all see the polls underestimated Trump's support in certain states - what you're apparently struggling with is that they still seem to have correctly projected the vast majority of states (including a couple of historic pickups), and Biden is on track to win handily regardless. You can't bleat about the polls being meaningless and then say Biden's a failure just because he didn't live up to them.
When all's said and done, Biden will have outperformed every presidential candidate not named Obama this century (I don't recall Trump ever being called a "disaster candidate" at this stage in 2016, but I'm sure there's a good reason for that). Presumably you think there's some other Dem candidate who could have obliterated Trump in the way you're suggesting Biden failed to do - curious to know who that would have been, and why they failed to beat Biden in the primaries. (Your comments about Harris suggest you don't know too much about the field, so I can suggest some names if you like)
Ultimately, all the hysteria earlier this week is down to the early results breaking for Trump, and the huge Republican advantage in the electoral college system. Ignore that noise, and you see that Biden has won a decent mandate. Unfortunately it seems like a few novices have been caught out by the events of the week, so hopefully you'll know better for next time.