For more complex GIS-data exploration, visualisation and research, I'd suggest QGIS. https://www.qgis.org/
It is not the most userfriendly (aimed at GIS professionals) but it does have a large, open and friendly community around it, making lots of tutorials, manuals, introductionary material and so on.
Edit: especially your type of "problem" is what qgis is good at: you have a CSV, maybe a postGIS database, some old scans of maps maybe; a government provided shapefile of the waterways and so on. And with qgis you can all project them over Google/OSM/Bing/Mapbox maps, mix, mash, filter, extract and so on. It is a desktop software, so publishing your result would probably mean "make some PDFs" or "render a set of PNGs" or so.
I'm a complete novice when it comes to maps, GIS, and all that. (Though I like to consider myself technically literate in general.) I had no problem getting started with QGIS for that stuff. It is fiddly, of course, but the software was clear and well documented enough.
It is not the most userfriendly (aimed at GIS professionals) but it does have a large, open and friendly community around it, making lots of tutorials, manuals, introductionary material and so on.
Edit: especially your type of "problem" is what qgis is good at: you have a CSV, maybe a postGIS database, some old scans of maps maybe; a government provided shapefile of the waterways and so on. And with qgis you can all project them over Google/OSM/Bing/Mapbox maps, mix, mash, filter, extract and so on. It is a desktop software, so publishing your result would probably mean "make some PDFs" or "render a set of PNGs" or so.