Do high pivot bikes still need idlers now?

Caveat: I don't know anything. I ride a short travel trail bike and I've not been in mtb for very long. I've ridden lots of bikes for a long time but I'm only 3 years and 2 bikes into the whole mtb thing so my experience is limited.

...but I think the idler solves more problems than just pedal kickback. The chainlines on a lot of high pivot designs don't seem possible without the idler. Granted, I'm not standing over or riding any of these bikes so I can't tell you specifically, but some of them look like the idler is necessary just to avoid the chain rubbing on the chainstay with a nice additional bonus of being able to tune pedal kickback with that idler placement. Take for example the Druid (which, by the way, seems to be priced really well right now...hmmmmmmmm). There's no way the chainline works from the top of the chainring to the cassette. The chainstay is in the way. The idler creates an angle of approach that allows for getting the chain from the top side of the chainring, around the chainstay, back to the cassette, and then back under the cassette to the bottom of the chainring.

I'd almost go the opposite way and posit that anti pedal kickback devices are less necessary on high pivot bikes with idlers because the engineers have often tuned that idler position to minimize pedal kickback.

All that said, I'm not sure the "pedal kickback" problem is entirely only pedal kickback as we think of it (the motion of the cassette via suspension movement pulling on the chainring and effecting suspension performance). I think the value in some of the anti pedal kickback devices is in providing a consistent deadband of non-engagement to allow chain flail to happen with less direct interaction on the chainring/rider's feet. If that's the case (the truth is probably a little of column A and a little of column B depending on the bike), then there's still some not-specifically-pedal-kickback-as-we-tend-to-think-of-it benefits to using anti pedal kickback devices.

But, like I said, I don't really know anything. I'm completely fine being 100% wrong with all of my assumptions. I've not ridden one nor ever felt the need for one.

My brain doesn't allow me to do much sleeping and it likes to spend a lot of time thinking about stuff when I'd prefer to actually be asleep. I spent a lot of time investigating these anti pedal kickback devices when I had 6 months off my bike via injury. No bike plus little sleep equals I learned a lot about a lot of stuff that doesn't directly apply to my life; anti pedal kickback devices being one example. My bike doesn't need one and I don't ride the sort of terrain that would call for one...but I've learned what seems to be a lot about 'em!

I agree. I think idlers and PK devices (like Ochain, Sidekick, etc) exist to solve different problems, but there's a lot of overlap in their Venn diagram.

"With these pedal kickback devises, do high pivot bikes still need an idler? Or is there still issues not able to be overcome by these devices?"

Short answer: yes and yes.

It depends on how high the pivot and rear axle grow.  A mid-pivot like Frameworks, they are right on the edge.  But anything higher you will never even out pedal kick or have the consistency of an idler.

Without an idler, anti-squat is insanely high. Makes for some bizarre pedaling.