Can someone please explain why not to use Brave browser ?

What hasn't been said as explicitly yet: It being Chromium-based means there's tons of implementation details that are bad, which will not be listed in any such comparison table.

For example, the Battery Status web standard was being abused, so Mozilla removed their implementation: https://www.bleepingcomputer.com/news/software/battery-status-api-being-removed-from-firefox-due-to-privacy-concerns/
Chromium-based browsers continue to be standards-compliant in this regard.

And this is still quite a high-level decision. As a software engineer, I can attest that we make tiny design decisions every single day. I'd much rather have those design decisions made under the helm of a non-profit, with privacy as one of their explicit goals, than under an ad corporation.

And Brave shipping that ad corp implementation with just a few superficial patches + privacy-extensions is what us experts call: Lipstick on a pig.