Start from the bottom and build a web portal that actually works properly. Fire your current developers and poach some from a decent company like Apple or Google. That way your website will work and your customers won't kill themselves - meaning you'll sell more subscriptions.

The new sign in "experience" is horrific, it has not fixed the problem just made the login more frustrating. Why not show the username and password field at the same time?

MS is supposed to be a legitimate organisation, please sort this out. Everybody I've ever spoken to that has to use the admin portal for 365 hates their life as a direct result of the horrific design and implementation