Not sure what Mac model you’re using, but on my 2011 MBP, it has the same limitations. The AirPort Extreme card (Apple’s term for the wifi card; in my case, a Broadcom bcm4331) does not work, but Ethernet works fine. Maybe try plugging into Ethernet or use a wifi extender or network bridge for now? As for brightness, Haiku displays at full brightness, and afaik, doesn’t have a Brightness preflet for the Mac.
In any case, there is other hardware you can run Haiku on; see the Computers compatible with Haiku (v2) thread for a list of working hardware as one example. There’s also other databases, such as BeSly, as well.