A great start would be to make the user space Adreno GLES libraries talk to the freedreno DRM backend. So one could use the QC proprietary GLES libs with a mainline kernel without rebuilding with KGSL.
There's a similar story here for every subsystem driver, where they insist on a brittle proprietary solutions (one branch for every chip!) that can't be upstreamed.
QC is not a low level employee lacking agency over their job description. They're a business that is free to set their strategy in response to risk and competition.
The less that QC upstreams, the more risk they incur, especially with tightening security scrutiny (e.g. 2021 Cyber EO requirements).
QC can also get disrupted by Mediatek doing a better job with Linux.
It should be if they're really serious about software support.