This is a difficult one because alignment is such a dumb concept to begin with. I literally makes no sense upon any inspection... but...

Artificer: Hmmm... this is a tricky one. There is mad inventor (chaotic) and then meticulous inventor (lawful). Good is definitely a stretch, but then so is evil. I'm stuck with True Neutral.
Barbarian: So, clearly chaotic (doesn't follow 'social norms'). This is probably the classic example of where D&D breaks down though. Even the word barbarian is inherently offensive with that offense drawing itself from the presupposition of cultural superiority. But that is where we are, so probably Chaotic Neutral.
Bard: Skews chaotic. Evil bards just don't... make sense in the D&D milieu, so probably Chaotic Good
Cleric: This one is literally meaningless. It is very deity dependent. That said, in the D&D world, the number of evil cultists does seem disproportionately high compared to the 'single good priest quest-hook', so maybe Neutral Evil?
Druid: True neutral. This is the easiest one on the list. The traditional druid is completely 'amoral' because their standards follow the whim of nature which is neither good, nor evil, nor lawful, nor chaotic. Putting it in those terms is silly.
Fighter: Another cleric. That said... most people are good-ish. Most players are fighers. Neutral Good. I made this up to fill up the chart below... obviously.
Monk: Lawful. Too disciplined to be anything else and that was a 3/3.5 requirement. Again, because of cultural influences, I'm going with Lawful Neutral. What is, is, how do I know what is good and bad?
Paladin: Finally. An easy one. Lawful Good. It is the whole point.
Ranger: Ooh... Chaotic obviously because of the 'nature-loner-edgelord' vibe. I'm guessing it falls into Chaotic Good
Rogue: Evil. Easily, evil. Actually, probably the easiest. Chaotic Evil. I mean... thief, assassin. These are evil lawbreaking professions.
Sorcerer: Chaotic (wizard counterpoint). I feel like we're going neutral here too. There isn't enough colour to the sorcerer to get the good/bad divide. Chaotic Neutral
Warlock: Evil. But we have a patron. Lawful Evil it is.
Wizard: Lawful (sorcerer counterpoint). Lawful Neutral it is.

Did we cover all bases:

Lawful Good: Paladin
Lawful Neutral: Monk, Wizard
Lawful Evil: Warlock
Neutral Good: Fighter
True Neutral: Artificer, Druid
Neutral Evil: Cleric
Chaotic Good: Bard, Ranger
Chaotic Neutral: Barbarian, Sorcerer
Chaotic Evil: Rogue

With a bit of contrivance...