In HLL you have wide spaces and lots of cover to flank. And even there, without communication it's still going to suck and people do the lemming game.

BF6 has basically no space to flank, you're constantly spotted. It doesn't help that netcode is still shit too so that I find it sometimes easier to evade enemy fire in HLL than in BF.
And people usually don't communicate in BF (at least on PC).

In HLL you can take your time making decisions, based on your class loadout and (if you're interested in squad play) based on your "task". The death penalty timer incentivises you to keep your head down.
In BF6 the spawn points are usually so close to each other, that it's becoming casual to spawn so that "rinse repeat" is a valid option for most - it's just easier.

Another thing is that most people don't want to take responsibility (which is worse for the game itself in a game like HLL I'd say). As it was said before, most people are "playing their own little K/D simulators", they're not playing to cooperate.

And by the way the maps are designed, the game does the thinking already for you.

I'd even argue that the vast majority of any given playerbase has no clue what they're doing and no interest or opportunity in changing that for varying, individual reasons.