Still have my 2tb Time Capsule also and the 802.11ac wifi still works fine, so I contiinue using that. But not using it for backups anymore. Yeah, it was always very slow. Also rather annoying in a quiet room when the disk spins up and accesses - it was loud! I had issues a few times with an alert that said the Time Capsule disk failed some kind of test, would be erased and the backups would start again from scratch. That convinced me it was time for a new solution.
As a replacement, I use an old headless 2012 quad Mini with four 5tb USB disks connected. You can setup any Mac as a Time Machine destination now in the sharing preferences (although it's so non-intuitive, I had to google it). I expect that Mini will die one of these days, will probably replace it with a newer/used Mini and just continue the same way.
But I also have BackBlaze for all my machines and make clones of all my disks regularly with Carbon Copy.
