I… what? OSX has been very keyboard friendly for as long as I can remember. Sonoma is buggier than previous versions, but you're been able use the keyboard to navigate most UI widgets except for the menus just as before.
that's a huge exception
https://support.apple.com/en-us/HT201236
And so is "open the help menu" which would take you right to the menu search widget, but that doesn't seem to work at all in Firefox or Electron apps.
Predictability is a core feature of UI design
Anyway, personally I use a better alternative to fully recreate the Alt+X to open a menu via keyboard maestro, so I've sovled the issue for myself, but it still is a core Mac deficiency contrary to the "OSX has been very keyboard friendly" claim