It's really not a difficult situation to figure out.
The NORMAL argument that exists is: Is this card good (as in meaningful, like something that justifies a purchase beforehand) vs Was the card "good" (as in exciting and enjoyable and having been worth to watch during and after). This is not an unusual argument, and anyone watching like the WEC events or paying attention to tiny fight nights for years and years can tell you that unstacked cards not only could still be exciting, but oftentimes WERE BETTER than the expectation that stacked cards had.
UFC 300 added the ADDITIONAL caveat of Dana seemingly promising some kind of parade-like spectacle of bells and whistles, so the expectation part of the argument got split into: "Meaningful" vs "Pomp and Circumstance"
I found a lot of the criticism of the card to be overboard, because it was very clearly a relevant and meaningful card all around. There was only 1 fight out of 13 that didn't have a ranked fighter on it, and it featured Bo Nickal fighting Brundage. The only other unranked fighters out of the other 24 were Kayla Harrison, Diego Lopes, and Jim Miller, who pretty clearly have some weight to their names.
But a lot of the criticism was of Dana's seemingly fabricated expectations on the Pomp of it all, because while the card was filled with good fights throughout, they were all fights that would have probably been booked on any other card at the headline or top. There wasn't something on it that was all that unexpected.
Now, I'm not sure what kind of shooting star anyone was expecting for this event, because anything surprising wasn't realistic, imo. Dana being a big ol' liar is kinda expected of a promoter.
And speaking of being a big ol' liar, Dana is purposefully conflating the original argument, saying that the event was amazing means everyone was wrong for talking about their expectations. Again, the argument became one of two different types of booking expectation were being argued, and he thinks action deliverance answers that question, AND is fully in on picking quotes out of context to serve that ego.
In short: Promoter misleads on how the card was going to be booked. The card ended up very well-booked, but not in the same way he seemed to promise, so people critique. The event was great. Promoter should celebrate a great event. Uses it incorrectly to suggest that the criticisms were wrong.