There are still "name" composers, and if you judge by volume of work some of those composers had a limited quantity.
Lerner and Loewe basically had four Broadway shows (Brigadoon, Paint Your Wagon, My Fair Lady and Camelot; Gigi was of course adapted from the film). Elton John has Lestat, Aida and Billy Elliot, and of course his own film music brought to stage in The Lion King.
Loesser had 5 Broadway shows and Finn had Falsettos and Spelling Bee. Including his additions to Victor/Victoria Wildhorn already has written 7 Broadway musicals (and God only knows how many countless others).
Tom Kitt has two musicals under his belt, and a third one arriving in a few weeks.
You're right that the Tony committee nominated two plays for Best Score, but they could have nominated original scores had they wanted to. Lysistrata Jones, Spider-Man, Leap of Faith and Ghost were all snubbed. People wrote new scores this year- the committee simply chose to ignore them.
Marie: Don't be in such a hurry about that pretty little chippy in Frisco.
Tony: Eh, she's a no chip!