I find the temptation to return to windows quickly overwhelmed by the AV software and security software.. and adware software and every other protection you need to load into the system to have some hope of beating the hackers. Followed by loads of just hating it.. !!
However there is no reason to keep "UPGRADING" .. I keep a version or two behind.. wait for the next version to come out which generally means end of major support for previous version.. and the one before that should just about be ok.
I jumped ship at vista.. so must be pretty near when you jumped. Snow Leopard at that time was a great OS.
A lot of the network trouble comes from recent changes to mdns responder.
I found the recent changes have made it difficult to get network drives in particular to be reliable.
I am happy to work through the issues with you.
I recommend the following.
1. All names short, no spaces and pure alphanumeric.. passwords same but can be longer. Apple moved to SMB protocol at Yosemite or Mavericks.. but High Sierra AFP is seriously depreciated.. YET.. due to failure to upgrade the TC it is still required to do backups. SMB naming is a lot tighter than AFP and Apple RECOMMENDED names.. are just WRONG.
2. Use IPv6 set to link-local only (assuming your whole network is not running full IPv6.. most are not). Do this for both wireless and ethernet.. whichever you use.. AUTO does not cut it.
Set IPv6 to Link-local only on the TC as well.
3. The TC must have a static IP.. this is no issue when it is setup as main router.. but is a big issue in bridge.. You MUST set the TC to static IP so it does not keep changing. You can do this via dhcp reservation on the main router or on the Internet tab of the TC.. note that setting both is good thing.
I found if you are forced to use bridge on the TC it is good to use DHCP server as well.. this is tricky setup so ask for details.. with full details of your network. When you have lots of iOS as well as Mac for as long as the airport lasts you can use it as the main DHCP server without double NAT.. this worked particularly well in my experience. Apple includes a bonjour sleep proxy in the Airport router.. no other router will.
4. The next bits are esoteric perhaps..
Make sure DNS in computer includes the main router.. not just ISP dns.
Make sure the search domain is blank or local. Not the ISP domain.
Make the main router domain local if at all possible. The TC is locked to local.. apparently and that causes some of the issues.
Super Duper is fine.. Apple integrated Time Machine.. and it is great software.. until you start using it on network.. then everything tend to go to pieces.
You cannot use the backup in the same way but it is totally wrong to say you cannot recover from a CCC or SuperDuper backup.. Of course Apple will not support it.. the 3rd party will.
5. The Mac must not include AV or security software or accidentally I'm sure adware installed.
Other things are elusive at the moment.
If you need help post again but include screenshots as that gives me a lot more clues as to your setup.