Many of Google’s map offerings can indeed be replaced with solutions based on OpenStreetMap, and quite a few sites and apps already have done so, especially with Google’s recent price increases.
However, note that OSM’s mission is to create a free map, not to run servers that can be used for free in an unlimited fashion. So while it’s generally fine to use OSM’s tiles and other services for some small-scale experimentation, there are relatively strict restrictions such as the Tile Usage Policy on the use of the services run by the OSM Foundation itself. The reason for this is simple: Having more people use our maps doesn’t cost us anything, but having more people hitting our servers with requests does.
As our servers are managed by volunteers and run on donations, they unfortunately cannot be an unlimited resource. So the main benefit of OSM in that regard is really the ability to choose from multiple service providers, as well as the ability to build your own self-hosted services or offline tools.