The website relies on something called tiles to display the map, which are prerendered blocks at different zoom levels.

https://wiki.openstreetmap.org/wiki/Tiles

In order to make any kind of devices able to visualize the map, the tile server will distribute rasterized tiles, which are easy to process even on a low-powered device. The drawback is that those tiles need to be generated by the server and more importantly stored. A tile of the entire earth zoomed out will not take a lot of storage, but the higher you zoom, the more tiles you need. If you don't put a higher limit to the zoom level ,it will take an exponential amount of storage on the server, which is a problem.

The main URL points to this:

That's odd, I swear it used to be able to zoom a lot more.

I would recommend using a dedicated openstreetmap app or service.

The real answer you wanna hear is:

Soon no more! As they will move from pixel based tiles to vector based rendering which will massively speed up load times and allow any zoomlevel you want.

https://blog.openstreetmap.org/2024/02/11/2024-announcing-the-year-of-the-openstreetmap-vector-maps/

osm-carto is for mappers, not users