I absolutely agree we need a holder but I'd far rather that holder is a passed who can tackle than a tackler who can pass. A small but, in my eyes, important distinction.I disagree with you about it being too defensive for a possession side. If you take the holding midfielder out of the equation then there are still 5 attacking players and that is in addition to our two full backs who are given lots of license to get forward. If that isn't enough attacking players then I would say that it is the personnel that we have wrong.
I think in a possession side it is perhaps even more crucial to play a holding player, this is because we tend to move the ball forward quite slowly and gradually gets lots of players forward, this leaves a huge amount of space for the opposition to exploit on the break if they win the ball when our team is advanced. With our marauding fullbacks and the huge spaces behind us, it becomes even more key that we play a holding player as that allows our centre halves to peel out wide and Dier to slot in to ensure we're not outnumbered centrally.
That role is the basis of every passing move going forwards - I think they need to be a good passer/reader of the game first and a defensive player second.