I don't think it's the case that there are two distinct sides, and that if you "support" the RF, therefore you criticise the Sussexes because of that.
THis is a predominantly British site, and many of us have been following and commenting on both family and institution for years.
And that criticism does not arise from (imaginary) partisanship, but as spontaneous reaction to latest words/deeds/publications.
So if William were acting as if he were the expert on homelessness then I would be agreeing with criticism of him for doing that. However what he is actually doing is being the one who highlights the issue, puts a new impetus to joined-up working amongst major players including 6 new pilot projects, and showcases the achievements of others. That I applaud.
The Sussexes, via Archewell, have made several grants to worthy organisations, and that is to be commended. I am far less persuaded by the tone of their public speaking, which lacks the depth that comes from long (or detailed/expert) engagement abd which also does not seem to showcase those who really do make a difference.
For example, the Duchess of Edinburgh has been working with charities and other organisations that seek to counter VAWG, FGM and rape as a tool of war. She is now respected for her knowledge, and how she can bring attention to the issue and those working on the issue in the countries she visits, such as Sudan and Colombia. The Sussexes will only get that respect in the same way as her and others, by that lengthy (years, decades) lead-in which builds both expertise and credibility.
They still come across as superficial/scattergun. That might change over time, as people see achievement. It won't come from just assertion