My problem with OSM, besides the lack of satellite layer, is that it doesn't seem to offer any (detailed) info of landmarks - just the name, sometimes not even that: for example, some churches are just marked with a cross.
If you want to try something really fun, install OSMAnd and download the Wikipedia maps, and then enable them I think in the "layers" option. I don't even think that's OSM data, I think it's geocoded Wikipedia articles. They show up on your map, and you can click on them and read them all offline.
If a church has its own Wikipedia lemma you can tag it. Most cathedrals have those. An image can be linked to, and of course the church website can be tagged as well.
For example:
https://www.openstreetmap.org/way/4532022
But in areas with fewer mappers tagging will be limited:
https://www.openstreetmap.org/way/390264609
It all depends on the local mappers adding and validating data.
By using the 'query features' tool on the right (the pointer with the question mark), and then picking the object you want from the list of objects in that area.
Other viewers of OSM data (like smartphone apps) can have different (sometimes easier) means of accessing that data. OSM is a database intended for use with many clients; https://www.openstreetmap.org is just one.
OSM is a very flexible data model. It's possible to add a lot of detail to things. Just because there isn't the data there for everywhere, doesn't mean it can't be added.
