We have toys that turn toons into naga and monkeys' That doesn't mean they are. My paladin just got Blackflame Daggers. Doesn't mean he's a dual-wield class.
"Look" means the visual, what we see. The iconic look of a DH is a bare-chested, blindfolded figure carrying warglaives, just as the basic image of a paladin is a plate-clad champion wielding a warhammer and a huge holy book.
Said books have even appeared on several of paladin's most iconic armor sets. I'd expect DH tiers to often reflect that lean, bare look we know them for, with chest pieces of minimal design.
Are you suggesting Death Knights didn't have expectation and baggage?!Blizzard isn't going to add a class whose design carries so much baggage and expectation that the deisgners don't have a free hand in its creation.
Blizz already powered through these arguments in 2008.The base concept of both would still be "power through dark powers" for both.
The spec themes of both would still be Demons.
The lore of both would still encompass Sargeras, the BL, Demons.
#1: When DKs were announced, there were forum complaints about the game not needing another "dark powers" class, since warlocks already covered that.
#2: DKs got a Frost spec, even though Mages already had one. They worked out to be quite different.
#3: Paladins already had intimate lore with Arthas and the Scourge. A DK class was not necessary to tell a story about a war against the Lich King.
Further thoughts on all three points:
#1: Monks have a wise, spiritual vibe about them. Shamans, priests, and paladins already had this identity in their respective cultures. Sharing hasn't hurt anyone.
#2: Are you implying that DHs would have a Demonology spec?
#3: Legion lore also runs through the racial history of Night Elves, Draenei, and Orcs, and ultimately shapes much of what has transpired in the whole franchise. Adding a DH class adds another avenue to explore some of that history, and could potentially fill in gaps in our knowledge about what happened between the Sundering and modern Azeroth history.
Mechanically, of course they are different. Their armor and weapons and fighting styles are entirely different. A paladin is literally more hands-on than a priest.
But in the history and institutions of Azeroth, the two classes are intertwined. From the Church of the Holy Light to the Argent Dawn and Argent Crusade, paladins and priests are frequently found side by side. Members of one discipline respect and follow leaders from the other, like Tirion Fordring and the Prophet Velen. Their methods vary, but their purpose is the same: heal the afflicted, protect the innocent, destroy evil, in the name of the Church/Naaru/Earthmother.