I don't actually want a choice! When I use Gnome 2 or Gnome 3 fallback mode, there is exactly one system monitor and it works. The extensions site lists 3 named system monitor and 3 pages of search results with similar descriptions. And my prior experience has been every extension breaks on Gnome version change. And usually they don't end updated so I have to go find another set of extensions.
I am one of those (apparently few) people who actually agree with the Gnome approach of less configurability and options. (Right up until one I use is removed of course!) As standard I do not need a large choice of system monitors, workspace managers, window switchers, volume menus etc. I need one good official one, that works out of the box and is still present as Gnome does its biannual update.