Not here to solve sexism is a dismissive excuse for problems that's mostly used to silence complaints of oppressive conduct or other issues in a community (such as an online forum), project, or group.
The mindset behind this rhetoric ultimately requires a firm belief that sexism/transphobia/homophobia/etc is of little importance in their community/project...
- due to absence of women/non-heteros/trans people/etc in the community/project
- ignoring or not realising that these people might be invisible or choosing not to participate due to hostile environment
- often assuming that participants with no explicit identity markers to be cis, hetero males
- dismissing or discounting the potential benefit of attracting more participants who are not cis, hetero, males, and more investment from those who are participating but feel unwelcomed
- due to (perhaps mistaken) belief in the community's ability to not be jerks (Not my Nigel)
- ignoring or not realising that oppressive behaviour can also be unintended
- and that it can and often does take place in personal correspondence or otherwise out of their own view
- due to lack of previous complaints
- ignoring or not realising that making a complaint takes a lot of guts in an environment that already feels unwelcoming, even hostile.
- Especially when discussing issues with invisible or potential victims, it is often seen with a Not my Nigel statement such as "we don't need a CoC because our people are nice people".
- It can be backed with appealing to the Broader issue, with the (faulty) logic that the issue on hand cannot be taken care of on a local level, or addressing conduct within only the project/community would be meaningless--and larger scale moves would indeed not be within the project scope.
- A classic excuse to silence discussion on sexist issues in Wikipedia.
- In the OpalGate incident, project owner meh repeatedly appealed that discussion on topics not strictly related to Opal were out of project scope, and explicitly deemed CoralineAda's Issue 941 (a complaint on off-site transphobic conduct by a core contributor) irrelevant to the project as well.