Impressive material. Legendary musicians. Great sleeve. It should have been a masterpiece...but it isn't. If you doubt this, just play it through & then play Chris Hillman's (admittedly pure bluegrass) MORNING SKY, issued 13 years later & light years ahead in sound quality, style & self-assurance.
To me, the main failings are: undisciplined playing, lack of a strong, commanding vocalist & a peculiar mix, which has Gram Parsons' vocals coming through the left speaker, Chris Hillman's through the right & the band in between at TWICE (truly) the volume. Not very pleasing to the ear.
Gram Parsons was undoubtedly a major, influential figure in the evolution of country-rock but I believe that influence seaped through gradually over a number of years following his death rather than in a blaze of glory during his lifetime. Just listen to Bernie Leadon's exquisite tribute, 'My man' from the Eagles' ON THE BORDER album or Chris Hillman's 'Hickory wind' from the aforementioned MORNING SKY.
Ultimately, I think the group, while full of youthful enthuiasm & bravado, were just too inexperienced in playing country (as opposed to rock) music to deliver the goods here (though better versions of some of these songs can be heard on the later "live" album, LAST OF THE RED HOT BURRITOS.