Personally I say GHZ is the only Sonic 1 zone fit to be in this game. All the others in that game are either boring as hell (Marble, Labyrinth) or were basically remade better in later games (Starlight, Spring Yard, Scrap Brain).
Like obviously you'd choose Stardust Speedway over Starlight. Yes, there's differences, but not enough.
Yeah, that's the problem with having more Sonic 1 stages in this game - they'd almost all be redundant with another stage already in Mania in terms of theme and gimmicks. Marble Zone is redundant with (and vastly inferior to)
Lava Reef
Hydrocity
Metallic Madness and Titanic Monarch