I haven't been following this thread religiously because I still haven't listened to either of the 2020 albums (I'm still pretty sensitive about certain styles of music after a personal tragedy, and indie pop is definitely one of those styles). But I just went through the last page and a half or so and I do think I have a general point to contribute:
I think "authenticity" in music is really hard to measure. I don't mean to say that there's not a genuine distinction between authentic and inauthentic music, because I think there definitely, definitely is, but that it's often hard to tell as an outsider who is being authentic and who isn't.
To me, an artist is being authentic when they are writing and performing music that they judge to be worthy, that fits their standards, that is something they themselves like and want to hear. They are being inauthentic when they are writing and performing music because of other considerations, usually because they think a certain style will take them on the fast track to fame and wealth, in disregard of their own standards and preferences. What this means is that to know whether an artist is being authentic or not, we have to have some understanding of their motivations. Sometimes we can get this from interview or statements: "I recorded this song because I thought it would be a hit" or "I didn't care if this would be popular, I just wanted to do a song I really love." Of course, in the latter case, we have to wonder if an artist is always being authentic when we say something like that. And when they're being inauthentic, it's rarely as explicit as the former statement. For example, bands sometimes say, "We just wanted to do a record that the fans would really love," which can easily be interpreted as an inauthentic statement, but it may not accurately reflect all of what's going on.
So even when an artist is directly telling you about their motivations, it can be challenging to discern what those motivations really are. But many people think they can discern an artist's motivations based on even less evidence, which I find very implausible. A singer works with a songwriter known for writing hits. Does that mean she's being inauthentic and going for popularity instead of following her personal standards? I say, no, it does not. What if she really likes many of those hits, thinks this writer is very talented with a style she likes a lot, and she thinks that he can help her write the type of music she would love to hear and love to sing? That is a motivation I would call authentic, just as authentic as the motivation behind a prog band that writes a 20-minute epic full of guitar noodling because that's the type of music they would love to hear and love to play. Same issue with a band who cuts their hair and starts dressing more fashionably. Are they trying to make themselves more appealing to record executives and MTV audiences? Or do they want to try out a different look? One motivation is inauthentic, the other is authentic, and it's difficult to tell which.
In sum: I think it's really difficult to tell a lot of the time when someone is actually being inauthentic, and a lot of music fans are, in my opinion, too quick to judge artists, especially pop singers, as inauthentic based on evidence that is entirely insufficient.