Not everyone has a 4K monitor and the new tab bar wastes a lot of vertical space.

Not only do the tab "buttons" themselves consume several pixels more that seems necessary, they are also needlessly padded above and below, for no credibly reason. What is the functional purpose and what can anyone even do with the wasted pixels above and below those tab buttons? What prevents those tab buttons from being the same height as the tab bar and why?

Please reconsider this design or provide/support a mechanism to switch off the waste.

Thanks

See https://blog.mozilla.org/addons/2021/04/19/changes-to-themeable-areas-of-firefox-in-version-89/

Have you tried disabling browser.proton.tabs?