I'm experementing right now making some Maps and have the same issue.
Using outline and anti alias assistand under Effects helps a lot and it's a quick work :)

Thank you, also a happy new year :)

Hi @kakiss4! Thanks for the advice, I did that a time ago with Paint.net but I'm really not a pro nor an amateur ;) Have a great Year btw !

Hi, some advice :)
Many Programs, like Paint.net , have some antialias option, it should help to smooth the outlines of the Objects for an better look :)