Holy cow, the clues were tough in this puzzle. I was fortunate enough to have entries into each section from a strange assortment of trivia type knowledge, or this might have taken much longer. But let me also say up front that this is really an outstanding themeless. I have almost no complaints at all!
I broke in with my first confident answer in a big way at 17A: Play and movie about a noted 1977 series of interviews (FROSTNIXON) - I've seen neither, but I remember reading about the movie. The NW corner was the easiest for me. With that in place, everything else fell quickly. I love 15A: Sly depiction, often (ACTIONHERO). It's a lovely hidden capital.
With SHIMON and HEXAPOD in place, 27A: 1983 7x platinum Billy Joel album, with "An" (INNOCENTMAN) was more than just a gimme for this inveterate fan. It's the last of his really great albums, with one of my alltime favorite songs, "Keeping the Faith".
Another bit of trivia knowledge helped me in the NE: recalling the RCADOME in Indianapolis. It was demolished in 2008, which is not as long ago as I'd thought. 25A: Composer of "Doktor Faustus" (BUSONI) is likely pretty esoteric for most people. I don't know this piece in particular, but the composer is familiar to me for his rather grandiose orchestral versions of Bach keyboard pieces.
For a few reason, I had to start over again at this point. I couldn't get the end of ONAKICK (too many possibilities, even after I guessed HAKE - and then took it out). 25D: Center of a blowout, maybe (BEERKEG) was really tough to see, even if you'd rejected the obvious sports-related feint. Fortunately 61A: One who won't give kids a shot? (ANTIVAXXER) was another relatively easy answer, and so I had traction in the SE.
The trio of answers in the triple stack here are the strongest in the puzzle. MARKOMEARA is a great name and certainly famous enough. And 63A: One who's gotten good marks? (SCAMARTIST) is a great clue. For a weird moment I wondered whether it would be a "scar artist" - is that a thing? I know there are some people out there into scarification as a form of body art, but... yeah.
43D: Urban lab transporter, maybe (PETTAXI) - woof. Literally. Turns out this is not referring to some kind of hirable vehicle to drive your animal to the dog park, although these exist in NYC, Google tells me. Instead, it's those crates with a handle you can carry your pet in. Anyway, nice reinterpretation of "lab" here. 45D: Noah's predecessor (STEWART) is referring to The Daily Show.
Finally, I broke into the SW when I realized that 38D: Herb of PBS's "Ciao Italia" (OREGANO) was not referring to a person. This is a rare instance of a reverse hidden capital! Also, I love CRANKCALLER. I did not understand this at all until I filled in the final letter (which I should have gotten earlier - KAY Thompson is a big hit in our household).
1A: Be on K.P., in a way (WASHDISHES) - C+. This is the least interesting of all of the long answers.