> Can't all of that, except teaching, be done by a secretary?

Not really, most of these tasks require some expertise. For exemple, committee meetings could be about recruiting colleagues and assessing their work or selecting papers for a journal or a conference. Grant writing requires expertise too...

No, committee meetings, which can involve things like setting the PhD curriculum, or deciding on faculty recruiting or retention, cannot be done by a secretary. No, grant writing, which is plotting the (often multi-million dollar) course for a lab, proposing science that has not yet been done and documenting those methods well enough and concisely enough for a review panel cannot be done by a secretary.

That'd require a secretary with a PhD. Looks more like most of it should not be done. But then, I have no idea how to change it.

Teaching is probably the easiest one to solve. Some kinds of classes should be attributed to teachers, not researchers (those are very different kinds of expertize).

It is increasingly common for large labs in the life sciences (25+ members) to hire multiple support staff (with PhDs) to help offset this load. This is in addition to positions like Senior Research Scientists (senior postdocs) who often serve as 50% "project managers" and 50% independent postdocs.