Have people's opinions always been so extreme or is it something new brought on by the internet,
It's absolutely been brought on by the internet, or more specifically, a few of the "big tech" firms have caused it, probably first and foremost YouTube and Facebook, but also Google and the rest of the social media platforms (Reddit, etc.) to an extent.
All of these platforms reward the content creators for engagement, i.e. whether or not people spend time looking at and interacting with a video / post.
They put absolutely no weight on the truthfulness or usefulness of the content. Just whether people click on it and look at it.
This is because advertisers pay for eyeballs and clicks - not eyeballs and clicks that come from the proximity of sane, useful content.
The (predictable) result is that content creators, in search of a bigger slice of the revenue pie, engage in an escalating war of sensationalism. Every opinion is extreme, everything is either the best or worst of all time, "god tier" or "shit tier", etc.
What's worse, is a lot of folks are willing to turn this from a game into a war. No rules or principles, just money. So the content itself is simply false. Sometimes they make obvious mistakes on purpose to get people to comment and point out the mistake. Sometimes they rate beloved things as awful for the same reason. Sometimes they just make stuff up out of whole cloth to get people riled up.
I am sure I don't need to point this out, but this doesn't stop with product reviews, it's also infected news and politics to a significant extent.