Is there any other series with as much of an identity crisis as the Darksiders series?
Darksiders 1: God Of War mixed with Zelda: OOT with Diablo-ish lore.
so, first of all, I'd not really compare either of them to God of War. the feel of the combat is way closer to DMC. but heavily simplified compared to either GoW or DMC as it's not the main focus of the game.
Darksiders 2: A looter hack n' slash semi-sequel?
Darksiders 2 has all the same elements of the first game, just with an added random loot system... which was mostly superfluous tbh. the combat is even more DMC like here tho, with more combos and generally better combat feel.
Darksiders 3: A character action soulslike
more like an action adventure souls-like. it is less character actiony than Darksiders 2. especially at launch it had ZERO character action genes. before they patched in an alterative playstyle mode, you couldn't even animation cancel... they added a separate mode that enables animation cancelling post launch lol.
it still has the puzzle elements of the old games... just toned down.
Darksiders Genesis: A top-down
ok, now this one is a spinoff, and that does count as much as Mario Party counts as a Mario game I'd say.
all in all, Darksiders 1, 2 and 3 are action adventures with varying influences. 1 and 2 are very similar, same concept generally, very Zelda-esque, just with a slightly different approach to loot. 3 then added the souls-like elements and toned down the puzzles a bit.
so I don't think it's all that weird. Zelda went through way more changes over the years for example... even 3D Mario games did. after all, Mario 64 and Sunshine were designed around hub levels with different missions, while Galaxy 1&2, 3D Land, and 3D World are linear level based games with minimal exploration... and Odyssey went full on massive levels with shitloads of objectives.