Adium is updated regularly and has been recently, and is open source. If that isn’t good enough, you are running OS X so just compile your own client of choice. Jabber is an ancient protocol used basically only in a few niche places, like Eve corporations, so don’t expect much in the way of client options for any OS, but there is also Trillian for OS X that can handle Jabber if you prefer, also still maintained.
Mumble is cross-platform and has a OS X client prominently offered on their main page next to the Linux and Windows ones. I haven’t used it in a few years but it worked perfectly fine then, and I am sure it works fine now.
All of these work natively under OS X and are snappy as any Windows client.
You seem to just want to complain. Yes, the OS X port of Eve Online has less than top performance, but it does generally work now thanks to the efforts of @CCP_Snorlax to get it running under Wine. If you really can’t handle the performance, Mac hardware can run Windows just as well as anything else so you can set up your machine to dual boot, or you can look into one of the cloud gaming offerings.