How many of our current squad can you see in the Champions League?
I think there are a number of ways to look at this and respond. On the one hand while I agree that there are a number of areas in the squad where we can improve, I'm not sure its a simple equation of looking at individuals and thinking if we switch this one out with another player we suddenly get better. For example you suggested looking at the spine of today and compare it to CL final 2008 (although I assume you mean 2007 when we went to Athens?):
To be honest I don't see what stands out by a mile.
But then if I look beyond the spine, I compare Johnson with Finnan, or Jose with Riise. Looking to the wide areas for the CL runners up I compare the likes of Gonzalaz and Pennant, to now Courtinho and Downing, to be honest I'm not sure we're that far behind if behind at all.
So maybe looking at depth as this is something BR has complained about: 2007 we had the likes of Arbeloa, Kewell, Garcia, Crouch, and Bellamy, while 2008 it was Arbeloa, Babel, Lucas, Voronin and Crouch. While today I do think our bench with the likes of Wisdom, Henderson, Shelvey, Sterling and Sturridge is a lot younger and less tested, I'm not sure its less quality, and surely more likely to improve over time.
Now again I do think there are changes to make, but just not sure they are clear or need to be wholesale. There are a number of players who have broke through as you suggest and helped us improve over last term (points, goals, position) but to suggest that is the maximum they can achieve I think is simplistic. Many of those youngsters are barely in their 20 so are likely to get better, and maybe much better, so its safe to assume the squad performance will as well. There are others who have not contributed to the level you'd hope or expect, which maybe good reason to look to upgrade, but many of those are not only new to the club but some have barely featured, yet get blamed for not being good enough . And lastly there are older players who I do think are not going to be good enough for a CL run or a title run, but maybe good enough to get us into the top 4. With these I'd suggest its a balancing act between what they can provide, how much we could raise from selling, and finally what the priorities of the squad are to make sure its balanced so it does perform at a higher level than the sum of its parts.