VXI11 is built on SunRPC and is used to tunnel GPIB over a network. The reason for an RPC (remote procedure call) protocol is that GPIB instruments can make asynchronous notifications to the host, like when there is data available in a buffer. Just basic telnet can't do this, unless you want the instrument to start randomly spitting out text at you or your program, that it then has to figure out has nothing to do with the command it's currently trying to issue. This is the same reason USBTMC is used over USB, just a VCP isn't sufficient.
LXI is a badge to demonstrate VXI11 certification.
I'd recommend updating your software to use VXI11... there are many implementations out there. I like
https://github.com/python-ivi/python-vxi11 myself, it's very easy to use although there might be better ones for your needs, as well as different ones for other languages. This doesn't use Visa or anything like that, it connects directly using SunRPC.