Here's the thing. A huge part of what the modern era is...isn't really about a lot of the things we THINK the modern era is about.
It's about things like:
- Farm equipment making it possible for a very small number of farmers to feed OVERWHELMINGLY ENORMOUS populations compared to anything prior.
- Automation and machinery making it so you can live a lifestyle once associated with being Quite Wealthy. This is the "washer/dryer/dishwasher/oven" effect.
- Metallurgy advancing far enough to permit the previous two things. Metallurgy is one of the few things magic in D&D really can't do much about; it can help, but it's not mind-blowing. (This is really the key thing that enables much of the rest.)
- Near-instant communication. Magic helps with this, but as it stands, it's not really enough to create the communications infrastructure needed for modern society.
- The discovery and harnessing of readily-available energy sources (mostly coal and hydroelectric) to produce electricity, which enables all sorts of other tools like the first two points.
- Modern medicine, which is one of the surprisingly few areas where the general cultural perception and the actual impact are mostly in agreement. We're slipping, though, because of stuff like the anti-vax movement.
Magic helps in a lot of ways, but in others it's not really
that much better than the medieval equivalent--and could actually
increase "medieval stasis" rather than breaking it. Imagine if the ultra-rich could have 90% of their need for servants taken care of by magic: wands that produce
heroes' feasts,
unseen servants that do the laundry and the cleaning and the baking and the brewing and the...etc., conjured footmen, "outfits" that consist of nothing more than a plain linen ensemble with an enchanted button to make it look like whatever you want it to look like, farms grown by a single paid druid and his entourage of
conjure animal helpers, etc., etc. Many of these things would entrench an ultra-rich-nobility upper echelon, albeit one where most nobles either are powerful spellcasters themselves or (more likely) are weak to middling casters but have a handful of domestic mages doing all this stuff (e.g. a staff of cleric, druid, wizard, and possibly a bard).
Because learning to use magic takes a lot of time and effort, and because (just as did happen IRL) many learned people will hoard their knowledge and resources rather than trying to share them and build up a community of interacting minds, it's quite easy for a society to fall into "medieval stasis" not because people aren't curious and pushing boundaries, but because social mores and structures, the devastation of war, and the hoarding of knowledge make it so that progress made in one place is sequestered in that place and dies when its developer does.
But, to answer the actual question of the thread, I will consider only spells of level 6+, since that's what the game functionally classifies as "high level" spells, the ones that are sharply limited. In alphabetical order, by spell level:
arcane gate (and similar spells)
globe of invulnerability
heal
heroes' feast
planar ally (and all similar "summon a powerful ally" spells)
programmed illusion
true seeing
wind walk
word of recall
mirage arcane
Mordenkainen's magnificent mansion
project image (especially if there are ways to raise the range)
regenerate
resurrection (and any better version thereof)
teleport (and any better version thereof)
clone
demiplane
glibness
mind blank
telepathy
foresight
imprisonment
time stop
wish