I think there are numerous aspects to it. One of the things I'm trying to get across is that the idea that your attacking play only comes from your attackers and your defensive play from your defenders isn't really how football works these days. Doucoure is playing as a 10 for us partly because he's good at keeping the shape, getting back to help out the midfield, cutting down passing lanes etc. If you take him out and replace him with a 'better forward' then you may lose that and that's a pretty big thing. Harrison and Lindstrom have played half the season as auxillary fullbacks, and even now the wide players are very much expected to get back and offer defensive cover. You can't just replace them with someone who has more ability on the ball but doesn't do the defensive side and expect it not to have an impact. If you want to play out from the back you need players who are comfortable doing that (properly doing it, not just not giving it away every time they get it but being comfortable getting the ball under pressure, breaking the lines with passes etc) and full backs are a key part of most teams attacks these days so you can only improve your attack so far if you have 2 who aren't very good going forward.
In short, no one thing doesn't necessarily have to mean the other, but there's an awful lot more to it than just saying 'if we sign better attacking players everything will be fine'.