Almost Reads Like A 'Mad Lib'
I can accept 'Lost Worlds' type stories up to a point. One subset of the Lost Worlds genre is the microscopic world - when done right (DCs Sword of the Atom for instance) it can be great. Unfortunately, this issue doesn't do it right. It's actually amazing that Doctor Doom became the scourge of the Marvel Universe given that most of his earliest appearances in Fanstastic Four are among the worst of the early issues of this comic.
This one reads like a 'Mad Lib' - you remember that old game where there would be a story with key adjectives and nouns left out, and you went around the room and everyone shouted things out, then you read the story back and it was goofy - yeah, this is like that. The Fantastic Four are bedeviled by Doc Doom who happens to be king of their Living Room rug. He shrinks them down and they get shrunk down even further and thrown in a dungeon surrounded by an ocean made of acid and swimming in the ocean are robot fish spies and Doc decides to sell them to a whole other microscopic race of Lizard men theat live on another microscopic planet that one can assume exists somewhere in the vicinity of the coffee table.
Of course all of this is an excuse to have an Ant-Man crossover - which is equally pointless considering Ant-Man doesn't really do anything noteworthy except give the FF some shrinking formula.
This is one of those issues with something corny, bad or wrong in nearly every panel, so I'm not even going to attempt my usual Silver Age silliness list.
The whole thing is a setup for a rematch with Doom next issue... joy.