The thing I consider before donating to Wikipedia is its gender bias - https://en.wikipedia.org/wiki/Gender_bias_on_Wikipedia
If anything, the Foundation will need to run programs to fix the status quo (e.g. outreach programs to potential authors who come from underrepresented groups or likely to write about underrepresented topic), so donating money (in addition to volunteering for outreach programs or contributing tech support) are some ways to help with that.
I don't think this is correct. Policy and culture are mostly bottom-up from the editors, and the foundation has no hard power except for extreme cases like banning outright harassers.
In addition, withholding money from the foundation does not cause any pressure at all to editors because they never get paid from that money anyway.
>> Diversity and equality don't cost money
Sure, but so far most of the efforts to improve diversity seem to come from the foundation rather than the editors, so punishing the foundation seems like the wrong option.