I think that's the crux of the problem with Islam. Hindu philosophy is so diverse and dynamic, that it keeps evolving with times. Caste system, sati etc were bad practices attributed to hinduism. But majority of hindus don't support them. At worst (or best), they say it was misunderstood or hinduism doesn't preach it. But they are fairly unanimous that things like sati and caste based discrimination are bad.
Islam starts with Muhammad and Quran was right (whatever they did) without any justification and try to keep justifying every act Muammad did and try to keep following them.
