SPO - Document Library (modern page experience) has extreme slow loading when grouping on a property

@Yannick Borghmans I'm having the same experience (2 years later).  I have not experienced this sort lag in the Classic Experience on the same site.  I wonder how much of this is the overhead required by using the React Framework or unoptimized JavaScript.

I'm working on a Proof-of-Concept in a free O365 E3 Dev License with over 450 documents.  I'm hoping that this is due to potentially less resources given to the Dev environments.  Were you on a Prod environment having these issues?  "Group By" enabled in Views in Modern Experiences is not usable while I'll be trying to sell SharePoint for User Adoption.  I will be forced to use Folders. :(

I'm also using Group By in the view and also the "Content Type" workaround: "/DocLibrary/Forms/View.aspx?groupBy=ContentType"

It's just clunky in Modern Experiences.