Soul Sickle didn't give CDR, but it did give lifesteal. It got dropped due to negative feedback, and I think the biggest issue with it is that it promoted the opposite of its intended playstyle (i.e. passive sustain instead of aggressive spellcasting), and risked leading into very boring gameplay. On one hand, it didn't really benefit champions who would prefer
in the first place, namely aggressive AD casters such as
,
or
, due to it offering little additional damage or spellcasting potential, and on the other its combination of health and mana sustain on a relatively cheap item meant that marksmen could pick it up early on, play super-passively with it and never have to budge from their lane. Bot lane has always run the risk of being overly passive and farm-heavy, as it has been in the past, and an item like this could risk bringing it back to such a state.
Honestly, I think the problem could be easily solved if they just traded the lifesteal out for CDR. A Soul Sickle without its 10% lifesteal and instead with 10% CDR and perhaps even, say, 5 extra AD (for a total of 25, up from its original 20) would appeal much more to mana-hungry AD casters and not go into issues of abusive sustain. The lifesteal could then just add itself later on as part of Essence Reaver's recipe proper.