Gmail's 'mark as read' feature unavailable

[goall]

Having been a user of Gmail for many years, I have always found the 'mark as read feature' useful while organizing my inbox. I however recently found that this feature is no longer available, meaning that I cannot easily reduce the number of unread emails in my inbox.

Naturally, I have been wondering why Google decided yo implement this modification that is evidently proving problematic to users.
Any ideas?