EDIT TO ADD: Here's the other thing that you gain if you treat a lot of D&D's magic narratively... you can become more thematic in the same way you can in say a game like Champions. In this case... you are a Telekinetic force mage. All Tenser's Floating Disc is, is another way of using telekinesis. Yeah, the game assumes they are distinct and individual spells that do not overlap... but if you look at the ideas narratively... you have a telekinetic force wizard that can easily move small objects with no real effort (Mage Hand); can move larger objects slowly (Floating Disc); can bludgeon other creatures using telekinetic force (Eldritch Blast and/or Magic Missile); can throw up telekinetic barriers in front of them (Mage Armor, Shield); can telekinetically bend light around themselves (Invisibility); can lift themselves up into the air (Jump, Levitate, Fly); can move themselves at superhuman speeds (Phantom Steed) etc.
In Champions, if you select all these different abilities and uses and narratively treat them as from one thematic identity, you get to buy them all at a discount. Unfortunately, D&D doesn't have that, and thus it is way too easy for a spellcaster character to just take all different types of spells randomly without having a theme. Now sure, some players will build pyromancers, or necromancers, or cryomancers or whatnot... but invariably they'll also have a lot of individual non-thematic non-narratively consistent spells too, because the game doesn't prohibit it or make it worthwhile to not select them. So even a devoted pyromancer will have the ability to create a Phantasmal Force illusion, because.. why not? Which makes sense from the gameplay perspective of D&D, but doesn't so much when you think about a wizard narratively. And I sometimes think the game (or more to the point, MY game) might be occasionally better served by treating magic more thematically, rather than "every caster can take every spell" that the game allows.
