I don't think the point there is about how "smart" people are?
With the reasonable assumption that it will have at least some issues - because very little, if anything, handles topics like this perfectly, and anything that works perfectly for one person may hurt another besides - it seemed like a fair description of how it could be received. You'll have the general public praising it, ignorant of any missteps or their degree if not outright defensive of them; we see this with TV shows all the time. But you'll also have fans - including trans people - who understand the issues but feel it still connects for them enough that they enjoy it overall. And then you're going to have some more left-leaning critics (and some of them will be trans themselves) who will examine it more thoroughly, and may find that the issues breaks the entire thing for them. That's not to say that they're "smarter", just that as critics they have to be, well, more critical than they may be otherwise. Though if the issues are small enough, it's quite possible that the third group is much smaller and those critics do still end up effectively in the second group (or something like it), etc.
I also want to say that this feeling really is happening already, and not at all unique to them or unfair to voice- the live reaction I saw on Twitter to the announcement was generally the same level of skepticism, frankly mostly harsher than they were. Saw some questioning if GLAAD was even really the best place to consult with on trans issues specifically, for example. The fact that they keep pushing this as a selling point didn't help.
And personally, now hearing the actual concept from the podcast, I think it's pretty fair to be wary. Prominently featuring (and advertising) a trans character is already a big undertaking. A story that seemingly involves you frequently seeing them at various times pre-transition, and making choices that sound like they could change how their family reacts to that, is an even bigger one. I would be very pleasantly surprised if they nail that, or manage to make the choices around it equally satisfying even if the result is uncomfortable.