It is worth to emphasize what has been said before here: Since Windows popularity is decending, they start to catch up with that attitude. Nowadays, for instance, you can open the terminal from every folder in explorer.exe -- this is exactly this kind of integration Windows missed for 20 years. Once they kick out cmd.exe in favour of something like Console2 (https://www.hanselman.com/blog/Console2ABetterWindowsCommand...) and update the toolchain even more than they did with PowerShell (actually integrating GNU/bash was a major step), developers will come back.
https://blogs.msdn.microsoft.com/commandline/2017/10/11/what...
But it's not a problem with PuTTY, it's a problem with Windows networking subsystem. Once you remove cable, the whole interface immediately goes down, IP address gets deconfigured, and all open sockets using the address get closed. (I was bitten in the ass by this when I had several Windows Server machines under my care.)
You'll get exactly the same with any other long running TCP connection.
> Remove the network cable while in an SSH session...
This argument seems a bit contrived. Is this honestly something you're concerned with on a daily basis? I doubt it.
> Try doing a port forward, and you'll need to dig around instead of just typing it into a terminal.
No, you don't just type "it" into a terminal. First, you have to lookup the command syntax if you haven't used it in a while. Then you have to type it in correctly and if your syntax is off by even one character, things don't work.
> Also aesthetically, PuTTy has nothing on Terminal.app or iTerm2 etc.
Aesthetics are nice but do you even have a tool like WinSCP? It graphically displays the remote filesystem over your SSH connection and then lets you open a terminal to the path you were looking at. I don't even have to type my password when I open a new terminal from WinSCP.
I say all of this having been a paying MobaXterm customer in the past.
These days I use ConEmu, WSL, and Bitvise (for those rare occasions I want to easily tunnel to the Windows side).