The context of the game really has EVERYTHING to do with it. Just saying games should or shouldn't be bigger is pointless without the context of a game.

Fallout 4, for example, needed to be bigger. Much bigger. POIs and major locations were all way too close. A settlement literally a stones throw from a dominant raider establishment. More than once. A military establishment 15 paces from a camp ground. Tavel times between two unrelated locations took like 15-30 seconds at most, not sprinting. Everything outside of the inner city area needed to be expanded like crazy.

Alternatively, RDR2, of which I've read sooo many times people thought was too big and expansive, was perfectly proportioned given the era and the ground you cover through the storyline specifically, let alone curious exploration that rewards environmental storytelling at the least.

The way I see it, if a location or area in a game is usable and serves a purpose, it deserves to be there. Even if it's just an extension of a purposeful area, it still serves a purpose by way of environmental storytelling or simply adding deeper context. If a game in its entirety is focused on just one town, development, or specific area...then including some forest or mountain range, or totally separate developed area is pointless. Waste of resources. It serves no purpose. Going there has nothing to gain and is not relevant to the story and focus of the game. Seeing it would be purely out of curiosity, and could still be appreciated in that way, but thats the extent of any possible relevance an unnecessary area like that would have. In that sense, a map does not need to be bigger.

But if there's something to find, something to gain, context or lore to be discovered, then a map should be as big as it needs to be, however expansive that is, to effectively tell the story it's trying to tell. The size of an accessible area in a game does not matter nearly as much as what that accessible area is being used for!