A reliable home network is key to a reliable HomeKit system. I cannot stress this enough. Every time you open the Home app, the app is going to ask for the status of your HomeKit devices. It is not uncommon to have multiple HomeKit Hubs and dozens or even hundreds of devices. Commands and device status updates are constantly being sent to all of the HomeKit Hubs and devices. If your home network is not configured correctly, you will experience unreliable HomeKit results. If you are seeing "Unresponsive" devices in HomeKit it is almost certainly something on your home network (assuming you are using well-respected devices).
I have a relatively large home (4,000 sq ft, three floors, dispersed laterally) with a relatively large number of HomeKit devices (over 100). I have nine HomePods, four TVs, and four TiVos and more iMacs, laptops, iPads, and iPhones than you can shake a stick at. It is not at all uncommon for us to be streaming multiple audio and video sources at the same time, and my HomeKit equipment works reliably and with good performance. So this HomeKit stuff works.
But home networking has become more and more complicated. For most of us, the days of a single combined modem and wireless base station are gone. Security concerns are rising. And now we have added Thread to the mix. The Networking section of this site contains recommendations that I have found useful:
What I Use
I use the NetGear Orbi RBK50 Mesh Wi-Fi System. It has proven very reliable and offers good overall performance. As I stated earlier, it isn't at all uncommon for multiple video and audio streams to be going on at the same time in my home, and my HomeKit devices have always performed reliably and quickly. This doesn't mean that other Wi-Fi systems won't work, this is just what I use, and I have found it to be very reliable for home Wi-Fi in general and HomeKit devices specifically.