Battery life is an area that may be difficult for smaller phone makers to compete on. I think Apple especially puts a ton of engineering effort and coordination into making iOS and their apps work efficiently with their hardware, reducing complexity, runtime cycles, and power consumption as much as possible, on top of already highly-efficient ARM hardware.
Over years of doing that (kaizen), the result is optimized hardware/software fusion with industry-leading battery life. But it seems like it takes a non-trivial amount of additional engineering time and effort to accomplish this, that will be difficult to match by smaller mobile tech startups.
I hope the open source community around Librem and Pine will be able to replicate that effort, but I'm not sure this kind of consistent incremental upgrade work is attractive enough to volunteer FOSS developers. And being maximally effective at it most certainly requires the parent company to coordinate the effort across hardware, software, internal teams, and external volunteers.
They don't run regular Android though, with Google Play, just the open source version with some Chinese marketplace. I have followed one (now dead) e-ink phone on indiegogo (forgot the name, sorry), and they wrote that Google does not let (black-and-white) e-ink smartphones pass Android certification, because they cannot correctly display the colors in their apps. So they will never run Google Play, and there will never be just e-ink phone with built-in regular Android and Google Play, sadly.
There is a hacky way to get Google Play on the hisense phones, but... ugh. That's too much hackiness for me.