There's no such thing as GIS maps. GIS is a Geographical Information System (by the way, it's not a GIS system). It's also the acronym for Geographical Information Science. You can do a lot by combining GI Systems with GI Science. One function of which is to make maps. But they're not a special breed. They're just maps, much like you'd make a map using many other tools.
Making maps (part of cartography) has always been a combination of art, science and technology. Get that magic recipe right and you'll make a pretty good map. If any of the three pillars drops short on quality or because of your ability to control them then you'll likely end up with a substandard map. GIS, then, is a core technology that supports cartography. It also does a lot more through its multitude of geospatial functionality. Of course, many people make maps using GIS because it's a core output. The map communicates results of analysis, illustrates natural and human conditions and tells stories. There's many different mediums of map that a GIS can support - web, animated, 3D, print, atlas etc. These are the maps. They're not GIS maps.
It's true that many maps made using GIS have a similar appearance but that's the fault of the person making them because they do not go beyond the defaults. It's why you can often spot a map made using GIS because the defaults can be like a fingerprint. If not modified, line weights, styles, colours and fonts all scream of your chosen map-making software. We therefore end up with what I think people mean when they refer to GIS maps - a data dump that lacks design and has common styling characteristics and a particular visual aesthetic. I'd simply call those crap maps rather than blame the software.
Defaults are a necessity in any mouse-driven maps (see what I did there?). They give people a starting point in the software and, over time, they really have improved tremendously. But you're still expected (advised?) to then apply some art and science to make something fit for purpose because, although defaults iterate and improve, it's pretty much impossible for a piece of software to know your precise requirements. Sure, sometimes a default is fine but becoming a smarter mapmaker demands that you critically evaluate what the software gave you and adjust if necessary.
So, just a heads up - if you tell me you've made a GIS map I'll immediately think it's an ill-designed data dump. If you tell me you've made a stick chart for navigating the oceans then you've just made the exception to the rule because that genuinely is a chart made of sticks (ht to Craig Williams for that!). I guess hand-drawn maps might also be a special case though, of course, pretty much all maps are made by hand, mediated by particular instruments.