It's a lovely chart. Your question is a bit fun, since the chart is clearly old and that's part of its charm isn't it?

I scanned through it looking for any obvious errors or things we've changed our understanding of a lot since then.

There's one picture of using Radium radiation in hospital treatments that seems very old-fashioned.

Define "better". If you mean more accurate, then yeah the regulated spectrum is much bigger now and more stripey. If you just want a rough overview of how the spectrum is organized plus all the other great stuff on the poster, I think this one is pretty unique.

It is copyright 1944. So it rather charmingly hand-waves away frequencies above 10 MHz or so. Such frequencies will be useful for television! And the plot stops at 100 MHz. (Nearly all radio used today is above 100 MHz.)

That said, much does still hold true. Longwave is still used by giant shore installations to communicate with ships. (Mostly by coincidence. Long wavelengths can reach submerged submarines.) The aeronautic band is still used by aeronautic non-directional beacons. The AM broadcast band is still AM broadcast. Some of the amateur bands are still in the same place today.

The physics and electronics depicted seem accurate. Its creators were clearly informed of the cutting edge in the 1940s; it depicts a magnetron, which had been invented about a decade before, and not widely used until high-power models were developed and then applied to radar c. 1940. A section about the health effects of ionizing radiation is conspicuously absent to my modern eye.

Well at the very top the speed of light is wrong :) It's now 299792458 m/s.

For the moment...

"Variable speed of light" - https://en.wikipedia.org/wiki/Variable_speed_of_light