I'll bite...

1 - Document Store (iirc, CouchDB was inspired by Notes/Domino)

2 - Replication - even past the 90s, it was one of the best tools for disconnected users

3 - Low barrier to application creation (it was about as easy as building something in Filemaker Pro)

4 - Easy publication of applications to the web (this was BEFORE 2000, so kind of a big deal back then)

5 - Administration of servers was pretty easy

6 - LotusScript (similar to vba) let you go much further than the prebuilt formula language (if you were willing to learn it)

Keep in mind, these benefits were available pre-2000, and in that time many were strong competitive advantages.

Replication was huge, we didn't even have an internet connection when I setup a application replicating between three suppliers and a bank.

Yeah, when I first started to use Notes, using modems over POTS lines to call HQ was still a thing, so that replication was a big deal.

Hell, I don't even think all laptops had ethernet ports back then either. In a lot of cases, you had to buy PCMCIA cards for that.

I realized how great Sametime was after I was forced to move to Skype for Business. The meeting functionality wasn't great but there were other great features. I sorely miss the button that allowed you to drag a rectangle on your screen and it would automatically send the resulting screen capture as a message. Not as an attachment that you had to open up, an actual image in the chat. Why can't skype figure that out!?