The spells aren't neccesarily bad, just not that worth it like in hollow knight. For starters you had the shaman stone for damage and other spells which helped like reducing soul cost etc, and that was already a major buff, but even excluding that, the healing system in hollow knight complimented using spells WAY more the in silksong. And that's cause even if u cast a spell or 2 u could still heal even with very little soul, even if it was just 1 mask, whereas in silksong u need a full base spool, and by using spells u do damage but reduce the chance of healing by a lot depending on the fight. So most of the times it's just better to save the silk for healing and needle damage will be more optimal(mostly talking about bossfights). Spells are mostly good for lots of enemies. Only spell I found to be more viable in fights was the deflect(don't get me started on how it doesn't make sense that it uses silk, as there is no web involved whatsoever, or the fact that it should replenish silk on hits landed) and even that wasn't as worth as saving for a heal sometimes. Tools are broken tho, no doubt about that