Sure, but generally because the aggregated polls were systematically off. You may be thinking of other examples, but the 2016 US presidential election really wasn't that bad of a look for 538, they had Trump at reasonable odds going into election night. It's not like he was at 5%, 538 pegged him at 1/3 odds as polls opened if I remember correctly.

So is the weather forecast though. 10% chance of rain tomorrow means, yeah it could rain. Doesn't mean it isn't useful.

It's on the aggregate of predictions that you can see the accuracy. If my weather app tells me hundred times there is 10% change of rain but it rains 50% of the time after 100 days, it's completely useless.

Same for FiveThirtyEight. They have been massively wrong on multiple counts.

You can check rain forecast results thousands of times and estimate how often they are correct.

Assigning probabilities to events that happen infrequently (US pres. Elections, wars, end of the world...) is bullshit IMO.

538 is pretty explicit about what forecasts went wrong and how they will try and fix it in the future