I don't know why anyone uses Tauri - disk space is cheap but having to handle QA and supporting quirks for every possible browser engine the users' system could ship with certainly is not.
Also if you haven't heard, disk space is no longer as cheap, and RAM is becoming astoundingly expensive.
So the footprint of the whole browser might be heavy, but each individual tab (origin) adds only a little extra.
Unfortunately both Tauri and Electron suck in this regard - they replicate the entire browser infrastructure per app and per instance, with each running just a single 'tab'.
And I share your concern for both disk space and RAM - but the solution here is to move away from browser tech, not picking a slightly differently packaged browser.