So, if you've seen some of the D&D 5e arguments we've gotten into over the last few months you've probably seen my dislike for challenges that amount to, in my word, "You Must be This Magical to Contribute". I'm opposed to the idea that playing D&D should absolutely require some amount of spell casting. That your party ABSOLUTELY should include a spell caster or two... or more really.
For a normal, textbook, standard party, yeah, there should be magic.
However, I hate the idea that every character should have magical abilities. I think there aren't enough non-magical character options in D&D. I wish spellcasting for Rangers was an optional ability, instead of saying every archer/woodsman just develops Druid-like spellcasting on his own somehow early on in their career, or at least that a non-spellcasting Ranger was a core option. I wish there were more non-magical, non-supernatural character classes (the Noble class from the D&D 3.5 Dragonlance setting would be something I wish had become core).
D&D should be flexible enough to encompass a wide variety of settings and play styles. The standard, textbook, typical party might well be a rogue, fighter, wizard and cleric, in a setting where there are lots of spellcasting priests and mages and spells get cast every adventure. . .but it shouldn't HAVE to be that way.
One of my favorite things about AD&D 2e (really the ONLY thing about it I miss) was the idea that it should be able to replicate a historic or pseudo-historic setting. The "green book" Historic Reference series that TSR put out for using D&D to emulate various historic periods, going from ancient Greece and Rome, all the way up to the 1600's, with everything from historic realism with absolutely no PC magic and the little magic that existed was super-rare. . .to a low-magic D&D version of history where there were wizards and clerics and monsters, just not with magic quite as common as it might be in Greyhawk or Forgotten Realms.
I definitely agree that there should be room in D&D for non-magical characters, and for a spectrum of magical levels of campaigns, from very-low-magic historic roleplaying, all the way to high-magic settings like Eberron and Planescape.