Honestly, in my childhood opinion, it was fine, just trying out food and drinks (whether from shopping or restaurants), testing electronics and arcade games, maybe even buying some toys or going to indoor play areas.
Though the novelty of it soon worn out gradually, taking a walk and peek at around these areas for anything interesting is good once in a while, even if you're not buying anything.
Edit: on sec thoughts, should I place this in the urbanism community? And just so you know, I'm not an American, so I wouldn't know what butcherism might occur in the implementation of malls.
You have been close and in terms of the GUM they are seen by some as precursors to shopping malls. I mean Corbussier's living machine does incorporate elements of them and is in fact very close to socialist ideas in architecture.
https://en.wikipedia.org/wiki/Unit%C3%A9_d%27habitation
Corbussier tried to incorporate living, but also social and communal functions as well as shops in a single building, the vibe is linked to brutalism and the concepts of taking those functions and qualities and thinking in terms of living spaces that have a central point for communal and commercial live was real existing socialist inspired or did influence those in the future i.e. the GDR and later soviet living quarters.
critical support for Lecorbusier for wanting to bulldoze Paris completely and build a huge airplaine runway in the downtown