I agree we need more goals, though there is only a tenuous relation between putting a goalscorer in the team and the team scoring more goals, obviously.
I agree Højlund and Zirkzee are only in their beginning of their carreers, and David seems a more moulded player despite only being some years older than the two former. Still, as they are more or less 1-in-3 game scorers now, as David was two years ago, they are to me not far behind him in that respect alone, as he is now on a 1-in-2 ratio. Indicating he is somewhat more prolific, but not that much - and how long will that last? To me, Højlund and Zirkzee seems to have other attributes that David lacks, while still being not far off him in goal scoring either. Neither are anything like bringing in a Kane, a Haaland or a Lewandowski. This goes for Toney as well.
Toney or David might get us a few extra goals more on their own in the short term, but maybe the team doesn’t score more. And the long term upside with me seems bigger with Højlund and Zirkzee. This is all just hypothetical, obviously.