You can, it's just harder, sometimes.

Very roughly spoken, the older the platform, the "weirder" stuff that happens at runtime gets in order to make the best of the measly hardware.

I'm looking at a many decades old C64 game right now, and the way I'm doing it is by having taken a memory snapshot when the game was in the state that I'm most interested in at first.

Starting with just the "binary" on disk would be much harder, since there's so much code that just loads, decompresses, initializes overlays etc. which isn't particularly interesting from an actual game logic point of view (though may be very interesting for other reasons), and only exists because the whole game just doesn't fit into all of memory.

There's also a bunch of loading and overlay magic at runtime of the game, but by looking at a snapshot of the game in the state that interests me, I don't have to dive into that (yet).