Possible workarounds:
Could the Fibery team perhaps adjust the formatting of Blockquotes to be more like this:
You could also insert an emoji/image.
You could get the above appearance now by injecting custom CSS –
.ProseMirror blockquote {
background: #eee;
border-left: 8px solid #bbb !important;
}
Though this will only affect your own browser, unless Fibery lets us define our own Workspace custom CSS.