I went to ethernet a long time ago. I still have my US Robotics modem in case I ever move out in the stix again and like yourself the thought of getting that up and running is scary.
Scary is the right word. If only there was a standard set of commands to send to the modem to make it act properly, but every manufacturer seemed to have its own idea about that.
Now that's assuming you get the serial line configuration right (remember how the UARTs in the modems didn't respond to arbitrary line speeds, but only to a certain set?), and the driver you're using isn't challenged by the data transmission speed you're trying to use (why did the built-in Amiga serial hardware let you down at speeds in excess of 9600 bps?).
Considering what you had to get exactly right, it was like trying to thread a needle during a hurricane (outdoors, that is).
Major customer support issue, if there ever was one. It was inevitable that the method of connecting to the internet had to change over time to something that wasn't subject to those countless variations on the customer's side. That's why we have the ISP supply the modems, and whatnot now. Also, Ethernet is a lot easier to connect to just about anything today than the serial modem port of old ever was.
I definitely don't want to go back to the dark days

And they were pretty dark before even PPP arrived. The ancient Amiga surfer package actually used SLIP to connect to the IBM network, back in 1996.