Potato potahto.D&D has long accommodated a variety of styles for handling non-combat stuff from complete free-form, to those who want mechanics, and those who mostly skip noncombat stuff entirely to focus on combat.
5e explicitly gives DMs discretion to adjudicate noncombat stuff through pure adjudication or roleplay or to go with skill roll mechanics.
D&D usually does not have a ton of mechanics for out of combat stuff, like a full in-depth social combat system, but many editions have stuff to handle most everything with mechanics if you want and D&D games with mechanics for combat and free form noncombat stuff work very well as D&D games in my experience.
"Accomodated" is a somewhat complicated word. D&D certainly has never actually handled non-combat stuff very well mechanically. By and large, D&D has left it free form. Which has the advantage of, as you say, getting out of the way for those who don't care. Fair enough. My point is, since D&D doesn't actually have much in the way of dealing with non-combat stuff, anything you do, or I do, or Bob does at an individual table is not transferable to another table because the reason it works for you or me or Bob, is indelibly linked to the specifics of that table.
Which is why, as per the argument about rangers currently, saying that the rangers at a table which mostly deals on the free form side of things, doesn't really apply to a stat-block, which is mostly focused on the combat aspect of the game. If your, or my or Bob's table has experiences that cannot be replicated, then there's no way to accurately state whether something brought from your, my or Bob's table will actually work. Whereas, if the table IS focused on combat, because combat aspects are not generally free form, then it can be replicated and the presumptions made very clear.
Well, I did say that this was a compromise didn't I? The stat-block, to me, if I was king of the universe, would strip about 2/3rds of that stat block away. Vecna's statblock, again, if it was made only for me, would have 5, maybe 6 actions total. But, WotC can't do that because people would lose their collective poop if WotC went that far. So, they go half-way and try to compromise. Those that want the out of combat stuff detailed in the stat-block still have some stuff, and those of us who see stat blocks as mostly just a combat element, get a stat block that is significantly easier to use than previously, even if it's not as easy to use as it could be.I don't know that that is what they are doing here.
CR 26 Vecna has prestidigitation, mage hand, and 1 action scrying. The scrying is quick enough to be used in a combat, but I am not sure that is something that will ever be used in the middle of a combat.
These seem more like things for a wizard NPC to use in a noncombat encounter (the cantrips) to show he is a wizard with casual narrative magical effects, or to give him narrative excuses to know what the PCs are up to (the scrying).
The statblock is mostly combat oriented, but there are non-combat elements there as well.
People keep talking about how things are changing so much and not respecting people's playstyles. Thing is, this IS respecting people's playstyles. This IS the compromise between the extremes. It only feels like a loss because people don't want to compromise at all and figure that the game should only cater to them.