Branding a SharePoint Site does not guarantee better User Experience. Branding and UX are often confused by the project teams. In my consulting journey so far I have seen many SharePoint branding failures and users are fed up with so called UX. Excessive branding is counter intuitive.
With SharePoint (both online and on-premises) I advocate to go with minimal branding such as Site Logos, Color schemes, custom CSS (if required) etc. No more extensive updates to Master Pages.
I once saw this quote somewhere on inter webs!
You don’t brand Microsoft Office Word! So why brand SharePoint online!!