All browser companies monetise you to some extent. Even Firefox does this a bit (Paid deals make Google is the default search, and Amazon search is also paid to be included as a link for example).
However the big difference is the private companies like Vivaldi, Brave etc monetise your data more and less transparently, plus the entire Chromium ecosystem is basically under Google's control. Manifest 3 will not be restricted to Chrome, it is being built into the Chromium project and will end up in Chrome, Microsoft Edge, Vivaldi, Brave etc. Chromium is a trojan horse project, used to push Google's priorities and objectives across the web, not end users.
The only viable alternative is Firefox based browsers. I use Firefox itself (aware of it's compromises and using a whole host of extensions), but there are also forks and projects that strip even Firefox's compromises back - LibreWolf in particular. For all the flaws of the Mozilla foundation, it is transparent on what it does to keep the project going, and the independence of the project compared to chromium is hugely important. Note Firefox is also going to support Manifest V3 (so that extensions can continue to be cross-browser) BUT it is also keeping support for the key APIs that Google is removing (i.e. the ability for extensions to use the block webRequest API which is foundational to current Ad and privacy protection extensions).
Vivaldi is no different to other Chromium based broswers; it uses the exact same Google controlled code base, plus it is doing everything it can to monetise you. You are the product; all these companies are stealing and financially exploiting your data and we're all just handing it to them on a platter for free and thanking them for fucking us over.