Unable to downgrade from icloud

I am unable to downgrade from icloud+ 50GB plan.

While the procedure given by apple support website is almost the same for MAC and iPhone, the final step of selecting DONE doesnt work. The button is simply not active to be clicked. Only the cancel button is active. Seems apple is trying to cheat people by disabling the downgrade option. Seems apple want another class action lawsuit by its abused users.

Why is it not allowed to downgrade?

I am using just over 1GB of the icloud so the space is not an issue.

I tried using iphone and MAC to downgrade with stopping on the same unachievable step of pressing the DONE.