I'm with all of you who want a faster speed setting beyond the one that exists. I have my Arena preferences set to fast-turn games only, and it's always a gamble as to whether the other player adheres to the recommended turn-time...
"Real-time • Fast paced = 0:41 seconds per turn (maximum 3:00)"
...or not. I mean, yes, using the red thumbs down will weed people out over time, but far too slowly, and it's just not enough. I agree that multitasking does often seem to be a culprit, since many a time I've offered a food or an egg via a sharing card like one of the Hummingbirds, and nothing happens for many many seconds, implying that they aren't actively watching the game when it's not their turn.
One of the things I loved about the old mobile Agricola app is that when you created a new game, you chose a fixed total game rather than turn times... so that, say, you chose 30 minutes: each player has a total of 30 minutes for all their turns, and that's it. So folks that go too slowly are simply forfeited at the end of their 30 minutes if they aren't keeping up. Way more effective.