There are already dozens.
https://gisgeography.com/google-maps-alternatives/
How many millions of dollars do you want to spend on your project before you run out of money?
Okay, that sounds much more manageable. But then could you please clarify? Your original question was about an alternative to Google Maps. But now you say you actually want an alternative to a different kind of gis mapping system. If you go into MUCH more detail about the context, we can give you better guidance.