Magic (whether they're spells or otherwise) falls into two categories;
1) Normal things done differently
2) Things that can't be done normally

The former covers a vast majority of spells. Any effect that only deals damage, lifts or moves things, transports items or creatures, heats, heals or any other process that can be done manually or by natural means. Yes, this even includes travelling to other planes in settings where portals and astral pools exist. Mage Hand or Telekinesis, for example, can be replicated by walking over to the thing and lifting or moving the thing. Likewise, Conjure Bonfire or Flame Sphere can be replicated by making fire the regular old "sticks and tinderbox" way. Just because the spell did it quicker, bigger, with different damage types or whatever, the effect can have happened whether the magic existed or not.

The latter covers those effects that no amount of regular action could have achieved. The truly impossible. Speak with Plants is one such spell. Without it or its effect, nothing can speak to the roadside shrubbery. Period. Animate Dead, Polymorph, Resurrection and Magic Jarwould also be examples of such effects. Even if one went on a quest to visit the underworld to retrieve the spirit of a dead loved one and implored their deity to return them from death, that deity is still using Resurrection (or similar magic) to restore their life. Similarly, without Animate Dead or a similar spell to create an undead creature, nothing is animating that pile of bones as an undead abomination (one might be able to create an automaton or machine out of them, but not an undead).

Category (1) magic doesn't matter and in sufficient abundance is just background noise; a setting detail as notable as the sand in a desert or trees in the forest. You could remove it from the game and nothing would really change. Eldritch Blast is just a magic arrow. Teleport is just a really fast travel montage.

Category (2) magic does matter, because it changes the possibilities of what can be true. Without magic that raises the dead, there is no quest to restore the queens life after her assassination, because such things are not possible, not even by gods. Without magic that creates undead, the Lich with his undead horde is just a creepy necromancer talking to corpses, slowly going mad with delusions of eternal life. Cat-2 magic changes the assumptions of a setting, not just what it looks like.