As a former Notes user (email, cal, plus apps for expense tracking, etc) - what did Notes in was the horrendous, non-Windows user interface. The second half of the article here is spot on, if anyone bothers to read it. Nice to see those old site ridiculing Notes, Jeff Atwood et al - a blast from the past!
As an end-user, I welcomed Notes demise.
And don't get me started on its god-awful local/offline sync behavior. Outlook ran circles around it. Hard to believe from todays perspective, sure, but yes, Lotus Notes was so much worse.
What was so bad about the non-Windows interface other than it wasn't Windows? I didn't have problems with using Notes email or developing apps for Notes. It had incredible workflow and database replication features. Blew anything Microsoft had at the time out of the water. When I was forced to start using Outlook, didn't care for it. Still don't think it's all that great. I guess Sharepoint is decent enough now.
Sure I guess if all you cared about as an end-user was email and Windows-like UI, then I guess I understand. But you were missing a ton of other things.
I was part of the small team that added Exchange Offline mode very, very late in the product cycle specifically to counter the Notes Local Replication story.
We were asked for something quick and easy, but decided to put the effort in to make it the correct way for the Exchange architecture.
The bulk of that code is still there 30 years later.