ARM has never been a good target. ARM has so many different architectures and ways to boot. Each of them being more like its own platform and needing different drivers. It has been a moving target all this time. IIRC Haiku almost booted on gumstix arm boards, but who even remembers them now?
It is starting to become simpler with UEFI, ACPI and devicetrees, ARM chips still need a lot of different drivers. The Risc-V port also made haiku a lot more portable which also helps ARM and other targets.
And the most important part: there needs to be a person willing to spend time and energy on it, it is a hard task and it is hard to stay motivated. So keep motivating and encouraging people…