CRISPR has been used to treat a rare genetic disease i.e. by injecting lipid nanoparticles containing the RNA into the bloodstream. OK we don't know the cause of ME/CFS and/or whether switching off genes would help but the technology interested me. https://www.sciencemag.org/news/2021/06/crispr-injected-blood-treats-genetic-disease-first-time
Hopefully genetic engineering will be able to prevent most diseases in the future. I think it's use is inevitable.
BBC Inside Science had a feature on use of CRISPR to treat this genetic disease. Apparently the fact that it affected liver cells made it easier i.e. since liver cells purify the blood and thus take up the lipid nanoparticles containing the RNA. Other cell types will be more difficult to target i.e. to get them to take up the genetic material - so that seems a big challenge. However, I assume this problem will be the focus of research, i.e. in more high profile diseases, and that might potentially help in the less prominent diseases. https://www.bbc.co.uk/programmes/m000xfh9
Going in an randomly editing parts of the genome will probably end up having lots of unintended consequences, such as maiming and killing ppl.
Not something I'm a proponent of i.e. changing pieces of genome without good evidence. Just pointing out that it seems that switching off/downregulating diseases causing/promoting genes is no longer science fiction albeit that the issue of how to target specific cells hasn't been solved.