The System is Antiquated
We can get angry and refuse to accept it, or we can choose to go with the flow. The fact is we often pass on talented software developers because they don't do well in coding interviews. This is rational when we ask them to write code pertaining to work they will actually do. This is irrational when we ask them to write code that has nothing to do with the job at hand.
Missing the Mark
look for something better
Hiring is Broken
accept the system and practice whiteboarding
Whiteboard Interviews Suck, Get Good at Them Anyway
Decide what's important to you at this time and plot a course. Get really good at code challenges and you will have more options to choose from. Not all options are the same, and maybe you don't want to work with organizations that operate like this. Focus your time and energy on getting better at coding, build applications and work on projects. This will mean you get less offers, but the ones you land may be more suitable.