If you’re unwilling to fix network issues, there’s not much Sonos can do about that. 

Note that network issues can mean either wifi or wired, it doesn’t make a difference. There are some that are wifi only, there are some that are both wifi or wired….

Have you tried the expedient of actually running a diagnostic after having an issue, and presenting that diagnostic number directly to Sonos, so that they can look at specifics, to see if it is indeed a network issue, or an issue with their product, or something else? Unfortunately, just posting here on these forums just will get all sorts of informed opinions, but without the hard data to look at, which only Sonos can do, they’ll remain opinions. 

This is a network or hardware failure issue. Without any system details we can’t help much. 

Soundslike you have a terrible router. Get a decent one.

Connection problems which appear suddenly are often caused by network problems, not Sonos problems.  The  typical cause is duplicate IP addresses.  These often show up after an update or power outage because a reboot requires the device to request a new IP, and the router, having lost track of current IP assignments, issues a new IP that is in use by another device.  To cure this, do the following:

Reboot/power cycle your devices in the following order:

Modem
Router
Switches or hubs
Wired Sonos units
Wireless Sonos units
Computers/printers
Wireless devices - phones/tablets etc.

Allow each device to come back up before proceeding to the next.  Note that you can permanently prevent duplicate IP addresses by assigning an IP to each device's MAC address in the router setup.  See your router manual for details.