The base graphics packages make the plots as ugly as the ones generated by gnuplot though. ggplot2 on the other hand has very pretty output. And the concept of grammar of plots just makes so much sense to me.
You can make plots look however you want with base graphics. ggplot2 users mainly use the default settings honestly, you get that classic grey background plot I personally find more ugly than the cleaner white background defaults of the base package.
That's only true IMO of the in-IDE plots, but actual exported PNG or vector graphics I think base R plots are pretty perfect, other than perhaps the default colour palette