I understand that you liked DOS 2, but I don't want to have any of it in a DnD game. And that's what ladan said they are making when they announced BG3.
And it seems you have the notion, that every character need a lot of actions to have tactical depth. I strongly disagree, you need lots of available choices.
Take chess for example. You only have 1 action per turn. But I think you will agree, that it's a very tactical game. Maybe it's not fun for you, because you can't set the chess board on fire (at least not as an valid action concerning the roles of chess), but that doesn't mean it doesn't have deep, tactical choices you can make.
I understand your position about DnD, and I already mentioned that it will be hard for Larian to walk middle ground in BG3.
Regarding actions - no, characters do not 'need' lot of actions, but it certainly helps. You need large number of combinations per fight in order to really have "tactical options" and chances for synergies. And combinations are influenced by number of choices AND number of actions per fight.
In chess, you have only one 'action per turn', but you have large number of choices per each turn ( 16 figures where some can move to 8-16 different spots, some to only 2, but lets say around 80 choices ). So in 4 turn 'fight' in chess you could theoretically select your 'tactics' out of 80^4= 40 million combinations. If we only look at 'meaningful' choices, ie those that make sense, then its much less, but still on each move you could probably on average consider dozens of potentially valid moves. Which means that 4-turn fight in chess still has 20k combinations - plenty to ensure that you need to *think* and tactically select best option, as opposed to just play whatever is available.
If we look at BG3, you have one main action per turn and one bonus action. Melee/ranged classes have only few main actions, and all have also just several bonus actions. So you have around dozen potential combinations of choices per turn, but that is total number - you have much less 'meaningful' choices, and you often end up in BG3 using same actions each turn, or selecting among 3-4 different turn plays at most. That means 4-turn fight in BG has just 256 meaningful combinations, not even comparable to chess.
Now, as I said, TWO things increase number of possible combinations: number of choices ( spells, attacks, cantrips, bonus actions...), and number of actions. But out of those two, number of actions has MORE influence.
Consider hypothetical game where you have 3 meaningful choices per action and 2 actions per turn ( BG3 is close to that ) - In 4 turn fight you would have total of 3^8= 6500 combinations. Now, if we double number of potential choices (spells, bonuses...) we increase that to 6^8= 1.6M in theory, but in practice not all added spells will be meaningful or often used, so its much more modest increase. On the other hand, if we double number of actions per turn, keeping same spells and choices, we now have 3^16= 43M combinations - about 40x more than if we doubled number of available spells/bonuses . And, while most of these numbers are just guesstimate ballparks to illustrate my point, incidentally those 40M combinations with 4 actions per turn is comparable to 40M combinations in chess 4 turns.
But since gamers do not play game by enumerating all combinations, above is just to illustrate that 'more actions per turn' is more potent way to increase tactical variability.
So I do believe that BOTH more actions per turn, AND more choices per action ( spells, attacks, bonuses ) all increase number of tactical options and make combat more interesting.
But apart from cold math, there is also my experience from games that allow 4-5 actions per turn: it is MUCH easier in those to use interesting but not very powerful spells, thus it is MUCH more natural to get synergies in such game. In DoS2, you have lets say 8 AP per turn. Your normal attacks are usually 2 AP, your stronger attacks/spells are 3AP, and smaller/helper/bonus spells ate 1AP. It is obvious that you have much more tactical opinions from start at each turn - do I use 2 big or 3 normal attacks? If I use 2 big, it may still be less damage than 3 normal, but can I add some 1ap helper spell like haste or clarity or ... ? So you end up not only using 2-3 attacks per turn, you also often have choice to use some smaller spell that you would RARELY use in BG3 if it means you must forgo your only attack.
In short, single main action per turn means you simply can NOT use smaller, more interesting but weaker spells/attacks, if you want to play optimally. While in DoS2 and similar games with multiple actions per turn you CAN, without intentionally playing worse than if you used just attacks.
I'm sure this discussion has been done elsewhere on these forums, as it is part of "like DoS" vs "true DnD", so I just wanted to explain why I think more actions are good.
But again, I understand position of DnD players, and I agree that BG3 *was* advertised as DnD game. It may be that I personally find DnD rules as negative thing or inferior to DoS rules, but I'm sure there are many DnD players who think otherwise. Also, even if I consider BG3 worse than DoS2, I still consider BG3 as good game - and even if Larian makes it more DnD I will still plays it ( well, except if they remove advantage on higher ground - that would be showstopper for me I guess ). But I also believe there are many more casual non-DnD players that may be lost to BG3 if it become more DnD.