John Kennedy Toole's 'A Confederacy of Dunces' comes to mind immediately. It’s more 60s than modern, but its influence is all over the place. Ignatius J. Reilly is the ultimate picaro, a slothful intellectual roaming a gloriously seedy New Orleans, clashing with everyone from factory workers to flirty old ladies. The humor is bleak, absurd, and cringeworthy in the best way, poking at American consumerism and intellectual frauds through a character who embodies both. Its posthumous success makes it feel like a modern cult classic, even if the setting isn't contemporary. The sheer vitriol and specificity of the satire keeps it feeling fresh, like a warped time capsule that somehow explains today's internet culture before it existed.
For something newer, though, I'm honestly a bit stuck. So many books bill themselves as 'hilarious journeys' but lack that true, episodic, outsider's critique of society. Maybe that specific picaresque flavor has just fragmented into other forms, like TV or serialized web fiction.