Dark Sky augmented their data with user reports and sensor data inside of the phones. There was a time during the summer of 2019 where I was able to impress friends by accurately predicting when rain would start and stop down to the minute based on the rain notifications I would get.

When Apple bought them and shut down the Android app they threw away all the data Android users were giving them and Dark Sky became almost exactly the same as every other weather API.

Perhaps in the US that is true, but "All" and "any" doesn't extend to other countries very well.

In the UK https://www.metoffice.gov.uk/ power a lot of apps, in Norway it is https://www.yr.no/nb . I'm sure most countries have their own weather providing service.

I don't believe this is true. DarkSky aggregated data from various sources. They also provided "hyper local" forecasts which were very accurate - I don't think NWS has anything like this. And I don't believe the NWS provides weather outside of the US - when I try to get the forecast for Mexico City, for example, I get "Data Unavailable For Requested Point" (https://api.weather.gov/points/19.4333,-99.1333)

If what you claim was true, apps would at least be consistent with each other. This couldn't be further from reality.

What I see in Dark Sky or Weather app is very different from what I see e.g. in Windy. Where I am now Dark Sky is almost completely wrong (neither real-time conditions nor predictions), while Windy manages to at least show accurate radar data and lets me make a short-term forecast myself.

It uses data from NOAA, among others.

https://darksky.net/attribution

Does it provide weather in Italy?

Detailed weather data and analysis is not free for many countries other than the US.