Rabelais said:
Instantaneous travel and communication? Check
Universal Literacy (at least in 'civilized' lands)? for pete's sake, it's spelled out in the PHB that everybody can speak and write their native language. Check
Governments organized on something other than familial relationships? Mostly so Check
Complex economies based on consumer goods? a hearty Check
In my campaign Waterdeep has more in common with San Francisco (circa 1900) than it does 14th-16th century Paris
It's those words, "in my campaign", that ultimately determine how medieval, enlightened, or whatever else a D&D setting is. Rabelais' approach, to make Waterdeep akin to 1900 San Francisco, is certainly valid, and there's nothing at all wrong with it. If you want to play that way, great.
If you don't want to make your world a fantasy equivalent of 21st century Earth, however...
Instantaneous Travel and Communcation: Not a chance. There are so few wizards and clerics of high enough level to cast such spells that there simply aren't enough of them to permit instant communication.
Most people walk, or either take ships, horses or wagons. You have to be 18th level to manufacture a carpet or broom of flying, and this is a setting where being 7th level is an exceptional feat. There aren't enough flying magical items to permit instant travle.
Universal Literacy: You're joking, right? Even many nobles and generals are illiterate. There simply aren't enough teachers, whether clerics or laypeople, to teach everyone how to read or write, especially when they have to constantly look over their shoulders for the next orc, goblin or bandit raid.
Governments based on something other than familial ties: Yes, in some places, although even then in many places women and various demihuman races may not be allowed to vote (the Yeomanry and Perrenland), not be allowed to own or inherit property on their own, being forced to step aside when a suitable male comes along, and generally be treated as second-class citizens (Furyondy, Onnwal, Nyrond, Sterich, Raik, Northern Aerdy, Ahlissa, etc.) Most governments are based on family ties, links of patronage, and other things-human and dwarven males can often have a greater social stature than other genders and races.
Complex economies based on consumer goods: Not exactly. Money is constantly being cycled in and out of the economy as humanoids, bandits and monsters kill people and take their treasure, and then adventurers bring it back. People might buy essential goods like soap, vegetables, tools or meat, but otherwise they try to be as self-sufficient as possible, even going so far as to use their own..."business" for fuel, and keep water sources pure for drinking, rather than risk polluting it. Only the rich can buy fancy consumer goods like jewelry, gilded coaches, slaves, exotic pets, or furs.
Then there are other social conventions:
-Someone insult you? Beat an apology out of him. Or, if you're a woman, send a champion to avenge your honor, unless you do it yourself. Given that most men will underestimate you, you can use that to your advantage.
-As the nobles, we're hiring you to kill those giants and get rid of them. And don't come back if you fail-if the giants don't kill you, we will!
-Catch someone picking your pocket? Feel free to cut off their hand.
-The Mercenaries' Guild: No women, elves or halflings need apply.
-Yes, this is Sunndi, and it like to make a big pretense of being friendly and tolerant to all. Unfortunately, even Sunndi, for all its goodness, doesn't always live up to its reputation. Just ask those dwarves who keep getting harassed and insulted everywhere they go.
-You see that woman with the big broadsword strapped to her back? Don't go telling her this tavern is for human men only...unless you want to end up like the last guy who got on her bad side.
-Peasants can't study magic, or use swords, spears, maces, or bows. It's the law of the land, even in the kingdom of Furyondy.
Not so 21st century now, is it?