Never said it wouldn't look significantly different, but downgrades are acceptable provided they're well judged. Doom was cut back substantially on Switch but was still a great experience.
MHW is nothing special graphically by PS4 standards, doesn't even look as good as Rise of the Tomb Raider.
Depends on what you mean by "well judged". Would it be "well judged" to create different versions of games altogether like FIFA 18 or potentially DQXI on the Switch or cut content from the home console versions via the level editor from Doom ?
There's way more to performance than just graphics. Physics, AI and level design complexity are all other things that can cause performance issues. The AI and the larger areas compared to RotTR look quite a bit more advanced ...
Switch's best bets are last gen ports, cross gen titles and games with high performance profiles already like 1080p60fps games from PS4 ...