Presumably modern researchers have a lot more information by now so their predictions are likely to be more accurate. As we get closer in time to it, it will become more predictable and obvious. You can't really have expected people at the time of the very first computers to have predicted the date of AI accurately.

Note the prediction has large error bars, with researchers predicting a 90% chance by the end of this century, but "only" a 50% chance within 25 years.

Anyway what's the alternative prediction? If you don't take predictions from the experts, who do you ask for predictions? Lay people? Just make stuff up? It's the best we can do.

One way could be to come up with one or more plausible, step-by-step stories for how AGI will be developed, then model how long each step might take to happen. This would open things up to discussion and criticism instead of having to take the word of experts as gospel. It still wouldn't be scientific, but at least it'd be closer.

I'm not arguing you should take the predictions as gospel. It's just an interesting and relevant datapoint. Maybe the only objective datapoint we have.

I went from being incredulous like you to apprehensive like Musk/Gates/Hawkings.

Let's just say that we would not be worrying about AGI if it weren't for the advances in machine learning, which has little to do with AGI research.