To be honest, I am a bit confused by your post.
The only reliable way to get Ebay to take action is via a case or by contacting Customer Services and explaining an issue. I have never been aware of the facility you say has now been taken away.
You can still report messages - at the top of every message, there are three dots, to the extreme right of the sender's name. Click on those, and the option 'Help & report' appears. However, as I said, reporting a message in that way is not a reliable way of getting help or action from Ebay.
For your particular issue, if you opened a case, returned the item and added the tracking to the case, if the item was returned to you, then Ebay would check the tracking on the carrier's website, see the seller had refused delivery but delivery was attempted, and refund you.
If the tracking does show attempted delivery, then use the link below to get a callback from CS.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)