Is there a better word for a news website besides "aggregator" (which implies the source only curates information) or "blog" (which implies the source only does opinion/commentary/no real reporting and also implies there is only one contributor)?
Not a word, but there is a phrase that is better than "aggregator" or "blog". You've even used it in your question, and it's not "online newspaper"; it's "news website"!
We have newspapers, which are news on paper. We also have news websites, which are news on a website.
The equivalence seems sensible to me.
[That said, ngrams would suggest that the world doesn't agree with me, as "online newspaper" is far more popular a phrase than "news website".]