Already back in '99, not leveraging 3D hardware was a problem for adoption. These days even more so, as not only 3D software but also 2D, audio and scientific software leverage GPUs.
[0] - https://discuss.haiku-os.org/t/plans-for-3d-acceleration/727...
The downside for Haiku would be that they're giving up on the original goal of maintaining binary compatibility with original BeOS software. But that ship may have largely sailed, anyway, with the decision to go 64-bit.
The upside is that it would reduce the number of different hardware devices that they would need to support in order for people to perceive it as useful software by approximately 5,367 orders of magnitude.
(Well, that and a bunch of rework to get over to the different hardware, ofc.)
I know that even BeOS 4 came on CD, and I think the free PE version of BeOS 5 was about 50 Mb (although that might have been a virtual hard disk image? It's been a few years...)