Having played both Zelda and dark souls for over 100 hours each on the Switch I think they are very different games. While there are some non-linear aspects to dark souls the focus is not on exploration but tactical combat.
Some elements feel dated in comparison to Zelda, particularly the physics, but the lore, world building, and level design in DS are some of the best I have seen (better than BotW IMO). Zelda has tighter and smoother controls and the ability to climb, swim, and jump (you can kind of jump in DS). The visual design in both are excellent, but DS has more interesting variety particularly of monsters.
I found DS worthwhile to play, but if you are looking for an open world exploration game it might not be what you are looking for.