They are showing more of Hellblade 2 tomorrow so hopefully we see something more to your liking.
Its all real high quality work, I'm not dissing or dismissing Ninja Theory's efforts. Just that if you know the techniques behind the trickery the artfulness of putting on a good show is where the "magic" really is. The key thing though is if you know that, then you're also aware of the costs and limitations involved.
Look at it this way. The sequence in that "gameplay" trailer is wonderfully done. BUT, if you consider how much work is involved in creating a sequence like that, and then factor in the amount of on-screen time it represents compared to the duration of a game, how much sense does it make to engineer it dynamically when there's no real need to do more than what we see in the trailer?
There's no benefit in creating dynamic versions of fixed-event sequences. It's just creating a rock for your back.
Thus the logical read I made when watching that was that its either composed almost entirely of pre-animated, choreographed sequences, linked and timed for optimum effect. OR in the final game its a much more dynamic boss battle, where the player needs to throw more spears in order to take the giant down, can miss their shots, need to actively find NPC's to arm them, etc, etc. This makes sense because you can afford to budget extra time for a major set-piece like a boss fight.
Either way, any sequence like that, is not gameplay. Because even if it uses the exact same assets, animations and shaders that the final does, its running without all the game logic in place (relieving stress on the hardware that can require trims and cut-backs) and has been directed such that it gives the most impactful visual impression. A game version will not have those luxuries.
Seriously, it drives me crazy because in the end what it results in is disappointment and anger that the gameplay version is less than what was originally promised. This is to noone's benefit, least of all the dev's.
The simple rule of thumb to use when judging gameplay trailers is to observe whether the balance of actions in there favours bespoke/one-off events or repeatable actions that can be applied across an entire game.
If its the former, its almost certainly an in-engine cinematic. If its the latter, its likely reflective of the experience you will have on the sticks.