The feature was underused and I think it did not serve it’s purpose well. Having hangouts in gmail is useful, having official emails and casual chats together mixes well. But in order to add an calendar event you need to specify the time, event name, notes if you write any, add meeting links and then mention the person. This is not true for every event, but I think if you are going to send calendar invites these would be helpful. To display these the UI would become clunky and sending it from calendar is easier and you would visualise the timeline. I have never used this feature, but could see why it was a killer feature to you
You don’t need to do all of that up front. Many times I use a meeting invite to suggest a time, allowing for the other party to adjust the timing, especially with someone you’re in contact with but wish to sync up. Once the time is set I’ll drop links in place. I like calendar but I find it clunky sometimes for similar reasons.