I honestly didn't think they made movies like this anymore.
Everything about this is great! I love those 1970's films about losers and misfits; movies like Five Easy Pieces, Midnight Cowboy, Scarecrow, The Last Detail, Alice Doesn't Live here Anymore, etc. This movie fits right in with any of them. It actually feels for the most part like it actually is from that early 1970s era. They even made the credits look '70s style.
Giamatti comes out with so many laugh out loud lines. His repellent, A-hole character grows on you and at the end, you feel deeply for his plight. There's a tiny bit of catering to modern sensibilities here and there, with scenes that reflect the view of the '70s as racist/sexist, etc. but overall they do not detract from the story. You aren't hit over the head with it.
I didn't have very high hopes for this. I wasn't that thrilled with the similarly '70s-set "Licorice Pizza" or the early 80's-set "Everybody Wants Some!!" I found too much postmodern ironic hipster touches, especially in "Licorice Pizza", but The Holdovers is about 90% a genuine 1970s slice of life drama.
It helps that they also featured my favorite film, "Little Big Man" in it, too.