it has been "beginning to change" for 20 years now. The fundamentals of how prestige/significance is allocated have not changed however, apart from the fact that there are a few reputable open access publishers like elife.
Of course! So few people in the world read these papers already, it is absurd to deny access to interested minds. Publicly funded research needs to come with open access strings.
Open access review and channelization is still an open problem. The for profit journals actually do provide a service of worth and note.
Beyond that, it is just the general time needed for society to adjust to a new way of thinking; people, scientists included, do not start questioning the status quo overnight.
The other science disciplines (mostly the life sciences), saw the AI/ML field greatly advance with their open research (e.g. arxiv, Github) and now want to copy it.
And yes, it was specifically AI/ML. Look at IEEE -- they're holding back the entire EE field. The ACM holds back the other areas of CS.
This thinking is slowly beginning to change, and the rapid growth of preprints in biology is helping a lot as well. There is growing recognition that journals in their traditional form may not be a great thing for science. There are a lot of different ideas about what the future of publishing and scholarly communication look like, and lots of experiments are being done right now.