It is not inherently pejorative, unlike predecessor terms that I heard often as a child, but are thankfully rare now (“bum” implying laziness or worthlessness, “whino” implying alcoholism, etc.).

U. Utah Phillips had a fun classification: You see, a bum drinks and wanders; a hobo works and wanders; a tramp dreams and wanders. Tramps are the intelligentsia of the traveling nation, people constitutionally incapable of having a boss, which means you've got to figure out other ways to get through the world. (He also loved singing Hallelujah, I'm a Bum and perhaps America's greatest champion of hoboes.)

For whatever reason, I've got a stronger association for "bum" to either laziness or incompetence than to homelessness. The strongest voice in my head for that word is post-war Brooklyn Dodgers fans yelling about Dem Bums as the team looses a close game.

I'm with you on language evolution; I'm glad that "bum" is no longer commonly used as a term for homeless people. It's not descriptive and definitely has a pejorative connotation.