The problem with soulslike is that the feature that meshes best with Castlevania is DS1's level design, and in 15 years they never managed to replicate the quality of that, which you would need for an entire castle. Nowadays "soulslike" amounts to rolling infinitely in corridors (or in a shallow open world) with particular care to PvP stuff. Not my cup of tea.
Aside from that, the platforming in soulslikes is extremely awkward and weak. And the whips in those games are terrible and do not resemble Castlevania's vampire killer at all (LoS also had this issue).
Well, either way its not like the Castles map are that much interconnected usually, tbh thats why we usually have to rely on teleports a lot. Surely some areas may connect at times, but not to the point we ever had plenty of shortcuts between dramatically distant areas of the castles, also because those map usually mostly develop horizontally, while Dark Souls, at least for the most part, privileges vertical exploration, which surely would work very well with a Castle like architecture if done properly, yeah. On the combat, the whips do indeed feel awful in those games, but i think if they were to make a game in this style of gameplay an arsenal of weapons as we usually have in most metroidvanias would be privileged, and i can see that work. The real problem i think is the pace is too different from both the exploration based vanias and the action ones, surely because of jumping, but overall because of a faster pace of action and movement overall. Tho I also think that if done properly it could still work well, but as I said before, id rather get a more action oriented game, even tho these seems to not be very popular anymore unfortunately. Again regarding the whip, i think Lament of Innocence had the best whip wielding gameplay we had in a Castlevania game, i honestly think it was extremely thrilling and you really got the feeling of swinging a whip, differently from LoS as you said yourself, where it just felt like you were swinging punches in a mobile game or something like that. Castlevania 64 was also cool with the whip i think, i wish the whips in the Souls game felt more something like that