A warning about Google's MyMaps as it works now, web-based rather than as an app: You need to have Wi-Fi or cellular data to move the map, zoom in or zoom out. We used to tell people (when MyMaps was an app) to open the local map in the morning while on their hotel's Wi-Fi and they'd be fine all day even if they didn't have a data plan for their phone or tablet. That no longer works.
On my last European trip (2019) I used less than 1 GB of cellular data per month. In the first month of my current trip, I used nearly 2 GB of data, and Month 2 is looking worse. The only difference in my data usage is that I now need to have roaming turned on when I'm wandering around. I don't always remember to turn it off when I go in a museum, which doesn't help help.
The amount of data I'm using probably would not be significant to a traveler who has bought a local SIM, but users of Google Fi like me pay $10 per GB of data when in Europe. I wonder whether that had anything to do with Google's decision to change MyMaps from an app to a web-based service.
I liked MyMaps. With a bit of practice I was able to build maps quickly even when I had dozens of pins (in a few cases over 100) for a city. You can add some extra info in the Name field, which is where I put hours of operation and sometimes a brief description (e.g., Tex-Mex buffet, contemporary art and crafts, etc.). There's also an additional field where you can add more text. When you click on one of your pins, a box pops up that includes everything you've entered plus the address and rating from Google.
Useful though I've found MyMaps to be, I'll be dumping it for one of the mapping apps before my next trip. $50 a year is too much to pay when there are other options, and the web-based Google Maps will cost me at least that much in 2022.
I'm not aware of any itinerary-building feature in MyMaps.