This "look-and-feel-as-branding" philosophy has now entered parts of the Linux community, as evidenced in this public letter to the GNOME community titled "Please don't theme our apps" asking Linux distributions to not apply custom themes to GNOME applications (https://stopthemingmy.app).
Personally I'm a major proponent of native GUI applications conforming to their platform's UI standards, and I'm also a proponent of users being able to theme their environments. In my opinion the purpose of personal computing is to empower the user. Users should be able to control their work environments and their workflows as they see fit. Unfortunately I feel that this philosophy of user empowerment has been slowly challenged, where the user experience is being controlled.