I was very specific for a reason.
"real person-level combat".
I didn't type those words idly. In real melee/arrow combat, you simply cannot behave like this. Casters standing at a distance might sometimes have the luxury to target specific people who they thought were threats, but they'd often be mistaken or operating on extremely limited information, or make very serious errors because they underestimated or overestimated people (this is down to the DM RP'ing them right of course - some DMs are clinically incapable of it).
A tank or pillbox can be "taken out" because it's not that capable of movement (we're assuming the tank isn't in an open field, because you're just stuffed). That's obviously not an equivalent situation. IRL, if you're armed with a sword, you can't just ignore another guy with a sword and go chase whoever you want. 5E doesn't have mechanics for that, though. No flanking, no firing into melee penalty, at most one AoO/turn, etc.
In reality, if you ignored a bunch of men with swords to try and chase down a wizard, you'd die with a bunch of swords in your back (or even just one). And indeed, anyone who has played a videogame that leans a bit more realistic absolutely knows this.
It's an absolutely unrealistic thing D&D does, that 5E makes far more extreme and obvious by removing all barriers to it and putting in "bag of HP" enemies that kind of require it. On some levels that might be smart - leaning in to a characteristic the game has - but trying to pretend it's realistic and putting in laughable 20th World War examples instead of medieval examples or fantasy examples is just unhelpful to understanding the issue, like it or loathe it.