... Oh god, I not just imagine the absolutely shitshow of a newbie picking MGSD thinking "Those are for kids, right?"
It could happen, but I don't think it's as likely as you'd think; for starters, there just isn't that much media coverage for Super Deformed Gundam. After all, their market space was aimed at capsule toys first and then models...except it's not like
all other Gundam isn't popular with middle school audiences, which was where they started. They're Bandai's Johnny Come Lately. I checked, and we
do still get SD Gundam television series sporadically, but they're absolutely competing for their audience with the Build Fighters line; the wiki says the peak popularity of SD was 1989 to 1993, which sounds believable (and there's almost a decade-long window where there wasn't, and BF was there instead).
On the other hand, there's nothing preventing a newcomer from picking, on the almost opposite end of the popularity spectrum,
Gundam SEED and thinking "Those are for kids, right?" Especially given the actual show's atypically bright hair and clothing colors, widespread jiggle physics, almost uniform
Hiraiface, and heavy shounen melodrama
. Half the mecha designs are even copied from already-established U.C. designs. But mostly that speaks to
SEED being stunningly popular, and staying popular, and the gunpla staying popular too; I have never seen anywhere selling Gundam models that didn't include at least
some gunpla from
SEED.
On the other hand, I'm looking at this from someone in my late thirties.
Gundam SEED is over twenty years old. But it's hard to imagine that's not what new audiences, especially young audiences, wouldn't encounter quickly.