There are three levels of graphics on the main galaxy map:
- No Zoom
- Medium Zoom
- Full Zoom
The first looks like an abstract representation of the galaxy, with little more than basic icons. This is completely intentional and MUST NOT CHANGE. It truly is a map, and maps don't have detail - they convey information, not graphics. Information on a large scale is aided mostly by simplification, not complexity. There's a reason that things like military maps use common, unchanging graphical icons/symbols for things, despite advances in technology. This view is all amount information, and, frankly, you should be spending 99% of your time on the galactic view in this mode.
The second view shows you enough details to be kinda cool - planets/sun/whatever now appear as small representations of their "actual" appearance, with modest graphical clarity. You can play in this mode if you'd like, and I do know some people do. But you give up a significant amount of "situational awareness" to do so, as models do not as accurately portray detailed information about what the item is at a glance (i.e is that a class 10 or class 3 planet? Can't tell unless I mouse over it...), and you inherently limit the total scope of your view (zooming in reduces the total picture.)
The last is for pure eye candy. It's by far the most useless, but is what seems to sell to fans, despite it having NOTHING to do with how good the game is, and actually being a detriment to most games, as the amount of time spent on that level of detail generally means other infrastructure/gameplay development is slighted. Civ 5 is an excellent example where there's completely gratuitous zoom which eats up a non-trivial amount of compute and time, for nothing other than looking cool. If you find yourself playing down at this level for more than a few instants, you really completely misunderstand the whole concept of a 4X.
Remember, 4X games are the computer version of a boardgame. The important thing is not what they look like (given some reasonable baseline), but how they provide a large-scale empire simulator.