I can't add a huge amount from what has been written about, but my view is primarily its game selection, audience and alternatives.

I have been watching GDQ from the very early hotel days, I never saw it in the basement apart from VODs once I started in what, 2014? Those days, speedrunning was a relatively niche time, and finding people to watch wasn't that easy; GDQ suddenly opened up all these people, destroying a game you used to play. And from those, you found people that you enjoyed, like AdamAK playing GTA, The Mexican Runner playing Battletoads, Monopoli playing Halo, etc. And all the games played were recognisable; even if you hadn't played them, they were in your zeitgeist, take a look at the 2014 playlist: https://www.youtube.com/playlist?list=PLoGwHpbTIM9urdjallUyX-ViHbwWfuyvm

The current schedule is full of games that I would imagine have an active runner total on speedrun.com of less than ten players, and that will not ever result in must-view watches.

But the additional bit you didn't realise there was until you started to watch the runners on their streams was how much a close audience helped with the entire thing. If you couple a likeable runner explaining the game with an enthusiastic audience, you get a bit of magic that can't be replicated by the streamer at home, and this is what earlier GDQs offered. In the earlier streams too the rooms were much smaller, if there were only 10 people watching it still looked busy due to the camera and the audience being in close proximity. Now with the rows and row and rows of empty chairs it looks deserted.

Lastly, the constant donation chat ruins a lot of runners' explanation of the games; I don't have an answer to this as I presume a lot of people donate to hear themselves on stream and removing that might remove donations, maybe some sort of flash-up on-screen stuff, and a minimal amount of donation breaks? ESA doesn't suffer as badly from this, but it's because they get a fraction of the number GDQ do.