There’s certainly a lot of racism in Hollywood, but it’s also the case that Chinese and other Asians make up a relatively small minority of the population, that the fact of racism may discourage them from seeking work in Hollywood, that first generation Asian culture is likely to disparage acting or showbiz as a career choice (and that those values may filter down in weakened form to later generations), the result of all of which is that although there are certainly plenty of good Asian actors who can’t get a job because of their ethnicity, if you put out a casting call you are likely to get any, many more non-Asians than Asians, such that even if you give preference to Asian actors, you may end up seeing relatively few of them.
That’s not to defend the situation, but it does mean that for a producer of limited clout working on a small budget, it might be next to impossible to get many Asians on your show unless you pitched it to the network that way and have their backing.