Celebrim
Legend
1e was viable for high level campaign. 5e is also viable. Both requires some work to make it work.
As far as I can tell, that's exactly what is being claimed by people like CapnZapp and myself, just slightly reworded. What is being raised is the idea that 5e is not viable for high level play using the published guidelines and as such requires that a DM do some work to make it viable. And by "some work" we seem to agree that it is an amount of work similar to what was needed to make 1e work above 10th level or so.
As for Isle of the Ape, you seem to be missing the central point, which is that Isle of the Ape pretty much proves that "some work" was required. Gygax's answer doesn't in fact prove the complaints wrong, as among other things it made rule changes to the game. All it does is show that you can continue to challenge high level characters provided you are willing to do things that the published material to that point didn't really do.
In all my years, in all my groups, I never met a single group that I could not shut down.
There is nothing less interesting for a DM to claim than that. The resources of a DM are infinite. The contest is not only rigged in the DMs favor, but the DM gets to make up all the rules of the contest. So there is no contest. If you are ever struggling to challenge your PC's it's because you don't really want to do so, either because you have a deep seated fear that doing so wouldn't be "fair" or a deep seated fear of being rejected if you do so. But no one is impressed by a DMs ability to defeat players. Of course someone with infinite resources and complete metagame knowledge can find a counter to everything.
Globe of invulnerability, Force cage, Wall (dome) of force and so many others to count.
Maybe so, but the number of published enemies for 1e capable of casting those spells probably could be counted on one hand. There might be something interesting to say about turning the tactics of the players against them, in the same way at low level a great reliance on burning oil might be met with enemies that employed burning oil. But one thing is certain, citing the fact that you could counter a high level character with globe of invulnerability, force cage, or wall of force in no fashion shows that 1e was viable out of the box and explained to the DM how to design appropriate challenges for high level parties so that DMs could walk that fine line you talk about. That highly experienced DMs could do so has been denied by no one.