> I don't understand why people pretend this is an acceptable solution for professional networking
Because it IS acceptable for many cases.
Many businesses don't operate in such a way as to have centralised infrastructure solely for providing internal networking, nor would they want to add the additional administrative or unnecessary routing overhead.
Even locations that would traditionally be considered highly centralised often have some form of dynamic network fabric as an overlay. Pretty much the entirety of cloud infrastructure runs on such systems, and they seem to do OK.
Also DERP relays having QOS that isn't controlled by myself and I have to hope to get bandwidth through doesn't exactly make me confident about the solution
Sure, but your data is only getting relayed through DERP servers if it cant otherwise establish a direct p2p connection. This can usually be resolved at either side of the connection - if you know about it (which is what the parent was suggesting could be made more clear).
As for your bandwidth concerns in the case of needing to relay, you can even set up your own relay (https://tailscale.com/kb/1118/custom-derp-servers), which would satisfy your desire to be more centralised (i guess you could force all traffic through it, but cant think why you would want to) while still allowing the flexibility of the overlay that tailscale provides.
I never said I had a desire to be more centralised. I just said that static IPs and open ports remove the necessity for hole punching/STUN. You can have multiple sites without a central and all use static IPs and open ports.
That seems like even more reason to use an overlay - it abstracts all that instability away and gives you a consistent, secure network regardless of what the underlying IPs are doing. Obviously peers can have static IPs too if you think that makes them more stable to routing changes (it doesn't).
You said "Dynamic IP addresses typically also have a forced disconnect at a regular interval.", which is false in pretty much every DHCP scenario I have ever seen.
A change in an IP lease should result in no downtime whatsoever, because addressing is not the same as routing. A routing change would have exactly the same effect on a static IP.
I then pointed out that an overlay network means you don't have to worry about that anyway.
I think you need to reread whatever comments you think you are responding to, as there is clearly something out of sync with your replies.
Because it IS acceptable for many cases.
Many businesses don't operate in such a way as to have centralised infrastructure solely for providing internal networking, nor would they want to add the additional administrative or unnecessary routing overhead.
Even locations that would traditionally be considered highly centralised often have some form of dynamic network fabric as an overlay. Pretty much the entirety of cloud infrastructure runs on such systems, and they seem to do OK.