I'm having trouble connecting to my chromecast in any apps. Sometimes it works fine and sometimes it just won't work. I can see that it is connected to my WiFi network and I've read the very helpful answers at chromecast-doesnt-show-up. After many resets and hours of fighting with my chromecast, I am wondering, would buying a new chromecast help my problems? It is a few years old, but I can't think what parts would degrade over time in a chromecast.
That could be interference of signals in your wifi/zigbee network that builds up with time, when new devices added or some devices select the same channel.
I also experienced problems connecting to Chromecast and ended up connecting the Chromecast to my router by wire using Cat5 networking cable. Moving to the wired connection improved reliability a lot, I don't even remember when I reset the Chromecast after that.
There's a special power supply for Chromecast sold by Google that has RG-45 socket and provides not just power but ethernet via USB https://store.google.com/us/product/chromecast_ethernet_adapter_gen_2