[alwaysbeconsing]

There's no reason keyboard navigation can't work in a GUI context. In fact it might be easier to define things like "up" or "forward" since widgets will often have a natural hierarchy with direct references to each other, so there's no need to parse anything to figure out what the "sexp" is.

[ParetoOptimal]

One problem is that macros currently work even in things like the settings buffer. If you change that to GUI, depending on the implementation, I'm not sure if that stays true.

For a settings buffer, maybe it doesn't matter. However macros working everywhere in your editor as a default is quite powerful.

[alwaysbeconsing]

I don't follow. Macros are literally just vectors of input events; if keyboard navigation works, then so will a macro that replays that navigation. (It is also already possible to record a macro that includes mouse events.)