Tony Vargas
Legend
Encounters shouldn't be mundane and humdrum, even if everyone in them is just beating eachother with sticks. It's meant to be a life-and-death struggle, no?My issue is that magic becomes mundane and humdrum for the players. When you're seeing three or four spells being caster every single round of every single encounter, it's pretty hard not to see magic as mundane and humdrum.
Where magic starts looking everyday is, well, when it gets used every day. Systematically casting Continual Light for a town so they don't need streetlights. Cool & imaginative the first time (c1975), keep it up and it turns you from mysterious Magic-user to Rural Electrification Bureau. That's been an issue with D&D since the get-go.
'Magic' in D&D has two quite distinct senses. Magic items, and magic using characters (spellcasting PCs, mainly). And it being 'ubiquitous' also seems to have two distinct senses. Use by PCs, vs use in the setting. A world where every PC cast spells in every combat and every non-combat 'scene' might be said to have 'ubiquitous' (w/in the PCs' storyline) magic, even if no one else in the world can use magic, making it a very low-magic setting. A world in which magic is used to clean & light the streets of every town, potions can be bought at the corner store, and flying ships are standard transport, could be said to have ubiquitous magic, even if the PCs are a gang of penniless rogues, barbarians & fighters who can't afford to avail themselves of any of that magic.Well, see, there's the trick isn't it? Which D&D are you talking about?
So the notorious High Elf fighter/magic-user was rare? Not anywhere I ever played 1e, sorry to say. And, wasn't 1e the edition during which "Monty Haul" was coined? And "Killer DM?"1e where magic really was pretty rare to see at the table, unless the DM started handing out a lot of magic items?

Casters had more spells/day, you had make/buy for magic items, sure.Or 3e where magic was more common
Caters had far-fewer slots, but also at-wills, you still had make/buy but items were far lower-impact, all-non-caster parties were viable. Kinda mixed, really.or 4e
Casters back to more spell slots, /plus/ at-wills, and every class can cast, but items aren't assumed to be as common. Again, mixed, depending on how you squint and look at "magic."5e where you see spells being cast every single round?
Sure. Then again, there's not as much pre-casting as in 3.x, when you could have just layers of spells on everyone. Thanks to the one mechanic that got slightly harder on caster in 5e: concentration.D&D has encompassed a range of magic level through it's history. Let's not forget that 5e has also made it very easy to cast in combat now. There are no AOO's for casting in combat anymore. There's no penalty for casting in combat at all.
Baseline? You mean like treadmill & bounded accuracy assumptions? Or as in amount of magic (items? casters?) in the party/campaign?D&D isn't a generic fantasy system. I totally agree. But, it was a somewhat more flexible system previously. 5e suffers some of the same problems that 4e did - it's very, very hard to adjust the baseline.