It's maddening that Google killed the MyMaps app several years ago so MyMaps is only available online. Except for the access issue, I love it. It has over 400 hundred icons you can select from and 30 colors. You can add to the default identifying text that pops up automatically for places you pin. I add the days and hours of operation and sometimes a few words of description ("20C art", etc.). I'm not aware of another app that has a lot of icons and colors to work with.
The inability to download the map and have it on your device as you walk around makes MyMaps much less useful. Once you walk outside the territory on the original screen, you'll need Wi-Fi or cellular data for the map to refresh. I keep saying I'm going to switch to something else, but I've gotten good at setting up MyMaps at home (the typing's easier on a PC) for the cities I'm going to visit, and it's great for planning my sightseeing itinerary when I'm in my hotel room. I use different symbols for art museums, other types of museums, historical sites, gardens, viewpoints, etc. It's easy to change the color of a pin when I want to flag a place as "been there".