Some great observations and (I can tell even before hearing them) some great covers.

Here's another perspective that fits with what you're saying: until the era of the singer / songwriter (starting around Willie Nelson and the outlaw group), most singers didn't write their own material (with exceptions, e.g. Loretta Lynn), but they chose material that would fit their image / style (e.g. Porter Wagoner or Connie Smith or George Jones). They would then make these songs sound original. "Bandy the Rodeo Clown" wasn't written by Moe Bandy, for example (but by Lefty Frizzell and Sanger D. Shafer).

The return to covers, as you so insightfully point out, is a kind of rediscovery of heritage. By the way, "Tennessee Whiskey" is originally a Linda Hargrove / Dean Dillon song. Hargrove (now passed) deserves to have a renaissance of her works. In 2005 (at age 56) she released an album of some of her earlier songs: Here's Tennessee Whiskey from that album: https://youtu.be/SqKZr3W56m8