Ya… Sounds like a new computer is the easy way to go. I am the same way with my main desktop in that if it is having problem and I can’t easily troubleshoot them, it gets replaced because I am not interested in the crap.
You are right that the 7950X and the new 9950X are not much of an improvement. They are a little faster, but like less than 10%. If you need big gains, you need MOAR CORES! 
Also, just an FYI (that you may already know) most routers put the 5ghz and 2.4ghz WiFi on the same logical network, even if they have different names. Likewise, the guest network is often (but not always) on the same network, just a different name/password. So even though the networks may seem separated, they probably aren’t.
You can run everything on the same physical network and have it logically divided using VLANs which are just what they sound like: Virtual LANs but you do have to have equipment that can handle it and set it up correctly.
What I’d look at doing in your situation, if you can, is similar to what we do at work. I work for a university, not a studio, but we do use Dante and other things that use Ethernet/IP but need to not be public:
For the Dante stuff, I’d have a dedicated physical network. Have its own NICs, own switches, and even make the Ethernet cable a different color (we usually use red). This does not get connected to a router anywhere, it is local traffic only, for Dante only. Not only keeps things secure, but keeps latency in check.
For studio systems I’d hook them all to a wired network on their own VLAN that lets them talk to each other, controllers, and the router, but no guest systems. No WiFi on studio systems, not even so much for security, but because WiFi cards have way more system overhead than wired cards (I’ve never found a satisfactory technical explanation as to why). Have a WiFi network in that VLAN for controllers, if needed, but that’s all that goes there.
If you can get away with it, don’t do a WiFi network for studio devices/personal devices of studio employees, but if you need one put it on its own VLAN with its own SSID, separate from the controllers. If it doesn’t need access to the studio wired systems, don’t give it any, if it does, only open the ports/IPs that are needed. Like if there’s a storage system that is needed open that up, but not the DAWs.
For guest systems, have a separate VLAN and WiFi SSID that they connect to which has only Internet access. If your router allows it, I’d make it a private VLAN, which prohibits them from communicating with each other if multiple ones are on it.
If you want something that’ll handle that pretty easy, I’d look at Ubiquiti. I have some complaints with their stuff, but it is minor, and one of the Dream Machines or Cloud Gateways should do nicely as a router/WiFi controller, their switches are VLAN capable, and their WiFi access points integrate nicely and support multiple SSIDs. You can then manage it all from one web interface. That way you aren’t chasing multiple devices around to make sure everything is secure and consistent and if you make a change (like changing a WiFi password or something) it happens to all devices at once.
It’ll also do security cameras, if you want that, and does a pretty good job. That’s actually what we mostly use them for (we use Juniper switches, but they are more complex and expensive).
); then there’s a 100% chance the internet router was bridged with the Dante network at some point.