Prime example of a flawed masterpiece. Symphony has a lot of bloat that isn't quite as present in other hallmarks of the genre. The game's arguably complex to a fault, and it's full of unnecessary stuff. 95% of the gear you acquire will end up serving no purpose but to clutter your inventory, the long & linear hallways offer little variety in challenge and make backtracking a bit of a chore, a good amount of the abilities you obtain only have fringe use-cases that are only useful in one or two rooms of the entire castle, magic spells and familiars are kind of useless - you get the idea.

All that said, something being "unnecessary" (in terms of not acting as a meaningful addition to the overall game) doesn't preclude something from being entertaining as hell, and Symphony triumphantly fights through the aforementioned bloat to carve out a space as a game that few others can compete with when it comes to the sheer sense of wonder and sense of discovery that it has. A lot of the weird edge case equipment and goofy joke items and obscure secret rooms merely exist just to reward someone who's clever enough to snuff out and experiment with the game's outer limits. Few other 2D games do so well at creating those incentives and going beyond a bunch of mandatory and bonus upgrades. The spinning bookshelf in the library, the chapel ghosts, the clock tower statues, the dark spike room... Not everything was important, and it sure could have used some more balance, but the way in which SOTN simply & ambitiously just provides more is extremely admirable and set new benchmarks for what all metroidvania games could provide. The effects of which are still easily felt in similar games coming out today, and for the better.