Brave is a Chromium Fork. And Chromium based browsers (and other browser as well) are well known for high RAM usage. This is unfortunately normal behavior.
There are a few things you can try like disabling extensions. But this will help only so much. I don’t use Brave on my iPad Pro (b/c there is no support for blocking cookie messages and it is way too buggy) but another browser - all based on Safari of course (there is no way around Safari on iOS). And despite it is an iPad Pro with a lot of RAM I often run out of memory when I have opened a few dozens tabs.
So yes, all modern browsers have a serious issue with memory usage.
Maybe there’s an issue with the hardware acceleration in the browser, Vivaldi and Edge managed to reduce the RAM usage by fixing the GPU hardware acceleration that Chromium has