I’m also using Firefox, but instead of ublock origin I’m using an extension called “Disable JavaScript” combined with the out of the box tracking protection (in strict mode). On my laptop with 4G of RAM, this works fairly well.

For the vast majority of news websites, running without js is a huge improvement to both performance and user experience. It even gets around a lot of paywalls.

I don’t think the sites that run slowly would be helped by a “lightweight” browser, since it’s not the browser itself that’s slowing things down, but the website. The only way to fix this is to remove those features from the website, whether that’s by disabling them, or using a browser that doesn’t support those features (eg a text-only browser).