. . . . why the pushback on ADS-B as something to augment overall situational awareness?
Two reasons, there are those who like to post that ADS-B is essentially Jesus bringing you a bottomless plate of zero-calorie bacon. It is a tool. I like tools, but I don't use a hammer, screwdriver, or an adjustable wrench to remove a Grade 8 nut. Some people love the "latest and greatest" even if it isn't an appropriate tool. As stated from the beginning,
in this situation, both aircraft were in communication with one another, both were aware of the other. Which brings me to . . .
Having ASD-B in some situations, possibly but not conclusively this one, is just "more noise". The CFI who was in communication with the Lancair pilot and heard him say he was behind her checked her iPad immediately before the collision. Now, to this noob, it sure seems like the 172 "owned" the runway. While not a requirement, I think the Lancair should have made a sidestep. That, combined with remaining low instead of climbing to pattern altitude, was fatal.
I am with
@RyanShort1 in thinking "Just a guess, but it looks like (the Lancair pilot) thought he could go full throttle and end up ahead of the Cessna in the pattern if he kept it flat and didn’t climb over the runway - or - as mentioned earlier, was trying to “buzz” the 172."
So, in the situation here, in no way could ADS-B have been a benefit. It may (or may not) have been a distraction. And it bothers me when people project their biases by making suggesting that all aircraft should have ForeFlight, ADS-B, electric starters, or stall horns, and that those who do not have those (and other "wonders" of modern technology) are a hazard. From my left seat, it seems that those who expect technology to replace competence are the hazard.
(I am in NO way saying that everyone who loves ForeFlight, ADS-B, electric starters, stall horns, or including engine oil in their empty weight is part of the problem.)