First of all, I am glad, we are talking on the level of facts now, otherwise this entire exercise would not make sense.

Let me make some additional remarks about the 5 aspects mentioned.

(1) Poor coverage in South America Middle East, India Asia and US (with loss of CO)

As others have stated, Middle East is about to be solved, India probably, too (but Star Alliance is not better with India either), Skyteam is, in particular when you count in soon-to-be Skyteam members GA and CI, by far the best alliance for Asia, and DL provides excellent coverage for the US. Regarding South America: Aerolineas Argentina will join next year and at least my Skyteam FFP has teamed up with Gol.
As it has been stated above: the only really weak point is local travel in Australia and New Zealand, but even for all international flights from Australia and New Zealand Skyteam has a better general coverage than any other alliance (unless you cannot do without the few direct flights Qantas offers, but out of BNE there aren't many).

(2) No top class airlines ( Five Star) in the alliance.
Yeah, I am sceptical about this ranking too. Even if it were a true indicator of airline quality, it is simply a fact that there are not many airlines in the 5-star category anyway. So this 5-star thing would only be a criterion for someone who happens to fly regularly origin-destination pairs for which one of these few 5-star-airlines is a reasonable option. For judging an entire alliance, the small number of 5-star airlines is a very bad criterion - a criterion that is not very much related to the practical consequences for everyday travelling.

(3) Poor upgrades and redemption availability for Elites compared to *A and OW
Actually, being a AF/KL Platinum member, I am happy about upgrade and redemption availability. For those *A and OW airlines that would make sense given my travel schedule, the upgrade and redemption situation is worse than on AF/KL.

(4) greater number of destinations served but fewer airport lounges (100 less than OW)
I never had any problem with missing lounges.

(5) Very few flat beds in business class across the alliance
The airlines with flat beds have been mentioned above. Additionally, KL is seriously considering introducing flat beds.


Finally: I am by no means a captive flyer. Actually, when I moved from Europe to BNE recently, I thoroughly and critically reevaluated all my FFP options (to the extent that my partner announced to leave me if I were to spend any more time on analysing FFPs :-) The outcome was clear: Skyteam is the best alliance for me, and this is why I still fly them.

So in sum: as I said above, it does not make sense to claim that Skyteam is the worst alliance. The only reasonable question is: what is the best alliance for YOU?