Preserve option to keep current UI: The so-called Modern UI is disgusting and objectively inferior

The so-called "modern" UI (euphemism for yet-another-shitty-downgrade) looks objectively terrible, and yields an inferior UX (e.g. smaller tabs, more space occupied uselessly, etc.) in every conceivable dimension. It is an unambiguous degradation, much like the new default "Dark 2026" theme.

Ideally, please never turn this patently awful design into the default UI; and if you do, preserve the option to switch back to the current UI (for those of us with eyes and the slightest bit of taste).