I don't expect the Secret Service to have act uniformly and instantaneously. I think there's some hindsight being unfairly applied here.
There was a fleeting chance the first loud noise really was a backfire or firecracker. The agents were familiar with firearms but not on a everyday basis. Sometimes when you have a preference for an outcome (ie: the first loud noise not being a gunshot) it colors your perception.
Like how Biden supporters (like myself) believed he was going to have an easier night, that there was no way Trump was going to take all five or six of the big states that he needed; but lo-and-behold he did.
Ten seconds over six is an indictment of the SS. Do I think they should have saved JFK? No, but there should have been a quicker reaction. Yes, easy for me sitting on my butt to say that.
As to Biden: I voted for him (Harris is completely unqualified for high office) but for a Republican Senator, i.e., divided government. That looks to be what we got. I didn't expect a Biden blowout but it looks like it's going to be something around 272 or so. He's going to have to moderate his policies if that holds up. The hard left (or hard right) won't like it but too bad.
As to the electorate: our liberal press and elites simply cannot think beyond race. They think black and Hispanics are over there; and whites over here. There's much more diversity within those groups than the liberal/left realizes or wants. That's a great sign for the country. A white party and a non-white party is not good for the country.