For the 1,000 time ... Deleting pics from iCloud

Not only photos occupy iCloud storage space , some other applications like notes , mails , calendars ... old back ups also occupy see https://support.apple.com/en-in/guide/icloud/mm7983cbca2a/icloud

See some articles to reduce the data https://support.apple.com/en-in/HT204247

https://support.apple.com/en-in/guide/macbook-air/apdb468896e0/2019/mac/10.14.5

https://support.apple.com/en-in/HT206996

https://support.apple.com/en-in/guide/system-information/syspf5a64aa6/mac

As per the article https://support.apple.com/en-in/HT209174

Use cloud-based services

Cloud-based services don't require you to connect an external hard drive to your Mac. For example, iCloudcan automatically store your photos, calendars, contacts, notes, passwords, and more. And it includes iCloud Drive, which can store documents, desktop files, and other files of your choosing. To access those files, you just need to be signed in to iCloud. Other cloud-based services are available from third parties.

You can directly delete photos from iCloud.com in small numbers hold shift key and click on the first photo and then the last one and click on delete icon .