In one aspect Planet of the Daleks is great. A return of Dalek vs Thal, with the other Skaro natives now from the future no less, with early space travel and trying to put a stop to a big Dalek plan. Clearly it’s another riff on the the original serial with a few tweaks here and there. Which can be done well. But the execution is pretty awful.
Things start out well. The Doctor going into some sort of healing coma that almost has you worried it might regenerate, Jo beside herself with worry, heading off into a mysterious jungle of a planet she has no idea about in the vague hope of finding something. That jungle being a minefield of dangerous plants and an invisible enemy stalking her. A spacecraft turns up with a rather violent crew.The first two parts are genuinely very watchable.
However, after that, problems a plenty start. Mostly it’s over written. Constant cuts back to the Daleks as they explain their plans, meaning that when we actually see it there’s no impact whatsoever. Everything that Day did right to make the Daleks scary again, Planet does wrong. Complications spring up with obvious solutions, and ten minutes later it’s like it might as well not have existed, as it was just treading time.
Once the Daleks are involved the Spiridons are pushed aside with nothing to do as well. The slave workers seems strangely loyal too, with some finding the Thals, and taking them captive, which just doesn't ring true for a race currently being experimented on. Even the one Jo befriends disappears, and only reappears to end a storyline that wasn't going anywhere in particular. Which is possibly a saving grace, as nothing is really done with their invisibility other than a reason of the Daleks are trying to steal it. The Spiridons themselves spend the majority of their appearances wearing purple rugs around them so everyone can see them.
It also heavily relies on the shortcomings of the Dalek design for the Doctor and the Thals to get away. The act of throwing a coat over the top of them is awful, especially if you do it multiple times, or just standing behind it. It’s pretty clear why the two arms were made to spin independently later on. If you want to keep your biggest bads actually that bad, maybe you shouldn’t point out all of their design inadequacies.
Though the speech about not glamourising war from the Doctor right at the end is one of his better ones.
At the time, Frontier in Space’s poor ending was excusable because it promised the story wasn't done, and with the Daleks now revealed we’re going to see some real action. That it devolves into yet another standard Dalek story is almost unforgivable.