Just a few point: The list of names - if we start with Al-Kindi (*801) and look up to Maimonides (†1200) we look at a time span of 400 years. So, if you let the Islamic Golden age end in the 11th century at least the later ones I cited were active after the 'decline'. Point is: The Islamic Golden Age wasn't a mayfly. It didn't stop with Al-Farabi's death in 951! There were still - if you count the 12th century as belonging to the Golden Age, for which there are good reasons - 250 years of quite busy activity in the whole islamic cultural sphere. And as people didn't live up to 400 years back then, strictly speaking they all weren't contemporaries. At all.
That most of the people I named took up the works of the greeks as their foundation is true: It makes my point that Islamic philosophy is a branch of western philosophy. Hell, even Wikipedida does list Islamic Philosophy under 'Western Philosophy'. (Not that this means much.)
I don't say that all was nice and cozy, but: Even Al-Ghazali with his fundamental critique is firmly sitting within western philosophical tradition and it's practice of rational criticism. His entire tretise is a reaction to philosophers. He is, shortly speaking, not thinkable without the ones he reacts to, he plays the same game. I mean, it's not like we don't count the Sceptics as western philosophers, because they were... uh critically questioning others before and contemporary with them.
Also: If you ask "is there anything x was able to contribute", then you are allowed to cherry pick. After all the question is "What are the cherries we should've picked there?". Your claim is, there weren't any cherries to pick, when in fact, they were there. It's after all not about whether one should accept shariah in general, but whteher there were lement in islamic ethics which we should have taken over. And yes: We should have seen taken from them the idea that women can own property, instead of only accepting that idea after women had to fight for it.
lastly, as to the influence of islamic humanis and Renaissance philosophy I refer to books like "Islamic Science and the Making of the European Renaissance" (George Saliba, 2007) focusing on the impulses the Renaissance got from the near east in regard to natural science and articles like "Scholasticism and Humanism in Classical Islam and the Christian West"
(George Makdisi, 1989), elucidating the relationship of Renaissance Humanism to mediaeval Scholasticism as well as the relation to the corrspoding movements in the islamic sphere, showing convincingly that Renaissance Humanism drew on Islamic ideas.
