Good read! I especially value a sense of exploration and surprise in games like these. Like you mention with Bobo the Cat, the best reward for satisfying your curiousity down side routes is always new puzzles, challenges or even just cool little locations.
I've not played a huge number of metroidvanias but my highlight would probably be Supraland - Very puzzle focused. Fairly linear overall but you move through wider areas, which themselves are dense and jam packed with secret areas and puzzles. The powerups are genuinely surprising and cool and recontextualise the world. By the end of the game your traversal options become entertainingly busted, well timed to not trivialise the game but to make cleaning up a lot of fun.
IIRC you played Hollow Knight but bounced off due to fairly barren level design? Apologies if I'm misremembering, but I broadly agree. I did really like the exploration in the game though - not really knowing the scope of the world, not always having a map at hand giving the actual possibility of getting a bit lost. I think with the various dlc included etc I probably didn't see a third of the game by the time I finished but in a way I'm always super happy when there's missable stuff in explory games like this, as it means there's stuff I might stumble upon in a future playthrough and be all Whoa! That's Cool.
I'm happy so many other people still also fondly remember Lyle in cube sector. I feel obligated to mention Nifflas's Uurnog Uurnlimited which feels like a spiritual successor (at least, intentially so in terms of mechanics and aesthetic), which has some really cool playful ideas. I dunno if it's quite a metroidvania but it's certainly a lot of branching interconnected areas, and is much about discovering what the various boxes, creatures and items in the world can do and using them to break puzzles.