For example, to view the JSON of:
https://www.wikidata.org/wiki/Q269728
You should be able to visit:
https://www.wikidata.org/wiki/Q269728.json
Currently you can find the json at: https://www.wikidata.org/wiki/Special:EntityData/Q269728.json which is practically impossible to find and is not linked in the "Tools" sidebar or anywhere else I can find. I saw somewhere that "content negotiation" might be possible to view the json format, but it is not practical in many use cases.