Later CompuServe became a reskinned AOL (seriously) and Prodigy devolved into a generic dialup service.
For a long time (maybe still?) you could access a terminal version of the CS interface over telnet. Basically all the same features as the GUI application, just in text.
There was also the original Microsoft Network (later shortened to MSN), which included a bunch of communities and boards. It was a Windows 95 application, and went through a semi-public beta then eventual release in parallel with the OS. You could connect through dial up or over the Internet, if I recall. I remember being impressed I could open two boards at the same time, unlike CS.
I remember getting personal developer support from Microsoft on CompuServe in the early '90s. MS engineers would actually send us some of their internal tools to investigate bugs. We helped them fix stuff in ODBC, and they gave us good support while we built what was, at the time, the biggest Visual C++ project they were aware of.
Obviously this kind of interaction is impractical today, but there must be some middle ground between it and what we currently see: companies shamefully abusing and hiding from their customers.
Many times I wondered "if they only knew MS Windows support on CompuServe relies on one intern working out of a frat house (at the UW)." I used a US Robotics modem running at 300 or 1500 baud without error correction. I had to write my responses in notepad and paste it in due to line noise.
Helping so many people every day was very satisfying and I am still proud of that work.