As you added sidewalk=yes to the parent roadand removed the information about a shared cycle route on the sidewalk you deleted, I fear your understanding may need a little refreshment from the wiki.

Separate sidewalks are mapped in a lot of places on OSM. The one you deleted had been there since 2014. People generally add them because they're useful for pedestrian an cycle routing. Knowing on which side of the road these features are is useful, as is the detailed information about accessibility like tactile paving and lowered kerbs.

You may think they map the mapping look messy. I would remind you that you should not map for the renderer. Deleting a feature which exists in order to "improve" the appearance of a particular map rendering is vandalism and likely to be escalated to DWG if it is repeated.

Of course I wouldn't add separate sidewalks to every street, I add the appropriate sidewalk=* tags to the parent street if mapping separate sidewalks is inappropriate. If you take a look at the streets around the roundabout, you will see that most of the available ways of tagging sidewalks have been added. On a lot of residential streets, which generally don't have crossings, they're effectively useless decoration, often added as a result of ill-advised projects using a tasking manager.

A shared pedestrian and cycle track on the sidewalk of a main road is commonly mapped as a separate way and the only justification to delete it is that it does not exist.

It does seem very odd that a mapper who spends so much time correctly adding access tags to non-public highways should be so ready to break cycle routing.