Thank you both for your replies!
So true! And I do agree that he bears some responsibility for what transpired, even if he was intimidated or coerced into it all. He is a pleaser, sure, but what I also see him doing, though to little avail, is trying to keep the people from going off the rails completely. He makes compromises in hopes (it seems) that they would eventually see sense.
Interestingly, in Ex. 32:4 ESV “he” [Aaron] took the gold and fashioned it into an idol, but they declared “Israel, these are your gods!” Aaron may have been a part of the “they”; he may not have. But he is certainly guilty by association and participation.
And, @alison, thank you for your reflections on typology, reticence, and enabling. I now have a new lens through which to read the OT! 
What I was noticing in my reading (after having reflected on the notion of “mediated messages” in another post!) were the degrees of relational separation from God of each character. Though God sometimes does speak directly to the people, he most often speaks directly to Moses. Or as the following chapter puts it, “…face to face, as a man speaks to his friend.” (Ex. 33:11 ESV) And the people, for their part, mostly speak with Aaron. So the relational thread runs a bit like this:
people <-> Aaron <-> Moses <-> the LORD
Furthermore, way back when God was calling Moses to return to Egypt and set the Israelites free (and Moses was not having it), it was Aaron who was appointed to speak to the people on behalf of Moses and God because he could “speak well” (Ex. 4:14).
Ex. 4:15-16 You shall speak to him and put the words in his mouth, and I will be with your mouth and with his mouth and will teach you both what to do. He shall speak for you to the people, and he shall be your mouth, and you shall be as God to him.
Ex. 4:30 Aaron spoke all the words that the Lord had spoken to Moses and did the signs in the sight of the people.
What an odd space for Aaron to be in! He’s not with Moses while Moses was in the tent of meeting or up on Sinai (that was Joshua’s role), he’s with the people. He’s in the dark in may ways like everyone else. I could really feel it when the people say, “As for this Moses, the man who brought us up out of the land of Egypt, we do not know what has become of him.” Neither did Aaron! He must feel the terror (and perhaps anger?) of abandonment along with them.
So, even though Moses does speak directly to the people at the latter stages, Aaron will always be the primary figure for the people. Again, none of this excuses Aaron’s actions, but his relative relational remoteness (compared to Moses) from God makes it easier to him to “err on the side of grace” with (or, perhaps, enable?) the people. His role comes into being because of Moses’ own terror of the people.
At any rate, I’m sure there are lessons for us here, but, as @michael reminded, I am glad I am not the ultimate judge!