One of my problems with #GoogleDocs is that it will block access if it thinks your browser is incompatible.
As a user of UserAgent obfuscators this is really annoying when someone wants to share a Doc with me.
#Nexcloud (with the #OnlyOffice plugin) does it exactly right, by warning me that I might encounter problems, but it is still up to me to decide if I want to accept the possible complications.
Kbin is developed by mostly one person, so yes, it progresses quite slowly.
But there is also Mbin with many improvements and much more active development.
I'm fully with you, that an API is still missing and would love to see it implemented in the future.