Datun we've had two new pools built here in the last ten years, both unisex changing. It's always been billed as "family changing" - we're an area with frankly terrible health outcomes, near the bottom nationally, and it's supposed to encourage families to come and swim together. I do think it works, actually, certainly the one I use the most is always teaming with kids and their grown-ups. Lots of dads and daughters, which couldn't happen otherwise. It's bright and light with staff walking through every 5-10mins.
Staffing is usually fine even during the later hours - ironically it was the older pool, with split-sex changing rooms that I felt the least safe in, because all the staff were men at 10pm.
I am always suspicious of cubicles with gaps underneath, though, and we try to aim for cubicles which are empty either side. I have been to a mega-pool in a nearby city which is unisex changing, and felt horribly unsafe there as it was much darker and narrower with blind spots, and no staff cleaning or patrolling. Ironically the "serious training pools" downstairs were single sex, open plan, and much nicer.
In sum I think they can work, but only if they're well-planned with a strong staff presence.