I have used Back to My Mac since it was released 12 years ago. It was a technology that was ahead of it's time considering it was for the "normal" Mac user. There was not another major OS that had this technology built in that was super easy for anyone to use.
As for the people that are complaining that it never worked for them, I have nothing to say to that. Maybe it was because I always used Airport routers and all Apple devices but it has never given me problems. I use this feature daily and it will be sorely missed when it's gone.
It was the ultimate tool that allowed me to keep my server upstairs while working on it through my other devices downstairs ... or even when I wasn't even in the house. On top of all that it was free and baked right into the OS! I remember one trip when I was in Europe, had a great internet connection, and worked on my MacPro for hours doing computations that my laptop couldn't.
For all of those people who never used Back to My Mac, I feel sad that you will never know how awesome this feature was. Almost as awesome as the vaporwear that would have allowed iDevices to transfer desktops between computers and keep them synchronized and no I don't mean in a doesn't-work-like-it-should iCloud Drive sort of way.
I know what you mean, however you can VPN in to MacPro when you are outside and then you should be able to access the entire home network. This may be the only free workaround. Good luck to you!