I'm not sure about typical front end development culture (the front end devs we have on our team are really very good), but I have been very surprised about how this generation of programmers in general choose to trust people and code. To be fair, it might just be some of the people I've met, but as an old guy, it seems to be more prevalent than I've ever seen before. I find that younger devs are prone to trusting code written by people they've never met before. If it's popular on the internet, it seems that it must be good. On the other hand, they seem to be
very cautious about code they get from their colleagues. As you say,
invented here syndrome. It seems like if the code was written by someone they know, then it can't be any good.
But I think a lot of that is a lack of confidence and experience. It's hard to talk about this without sounding like a gigantic ass because no matter how I put this, I can't find a way to express how much I really respect other developers. However, I've noticed that there seems to be a big reluctance for actually reading and appreciating the code in the tools people use -- almost as if there is some magic seal on the code and despite it being open source, we are not worthy to gaze upon the code. I think there is a fairly large amount of hero worship going on and a kind of herd mentality. To question the laws that were handed down from on high is blasphemous (almost literally). It is to the point where many people feel that they are transgressing badly if they even deviate from the "community approved" coding standards. Thank god for auto-reformatting tools is all I can say!
When these same people see their colleagues, they realise that it's just some other goofball like themselves. Their colleagues are struggling, making mistakes, rewriting, grinding away. So I think there is a kind of group impostor syndrome going on where they think, "Well, that guy isn't that much better than me and I suck!" What they don't realise is that their heroes in the FANG companies and their nameless horde of community members are just goofballs too -- struggling, making mistakes, grinding away.
I think as well, we often see projects and people fall from grace. Some project grinds to a halt, or the horrible problems it's had from the start become more obvious to the horde. And then all of a sudden it's, "That guy is a joke. Only morons would use that framework. All the cool people have moved over to <some other equally flawed thing>". But again, I think it's just part and parcel of a lack of experience and confidence. Most young devs are secretly, desperately hoping that somebody out there knows "how to do it right". They get disillusioned quickly when they discover that their heroes don't know how to do it right.
And of course, nobody does ;-) But that's a hard message to sell.