They play in different positions though. Lucas announced himself as a volante if I remember the right term i.e. the midfielder who played alongside the defensive midfielder and circulated possession apart from helping out with the defensive side of things. Soon after he went on to become a full defensive midfielder and given his role in the team and the importance of keeping possession, I think defence of Lucas is well justified.
Right, but the criticisms are still very similar. Those who didn't think he was good enough, didn't think he was good enough as a footballer, regardless of whether he was a volante or an all out DM. I still think we're not using Lucas in a way that maximises his full potential but that's for another thread.
Henderson plays a far more advanced role and if he is being groomed to play Lucas's role in a few years fair enough but I doubt that is the case. His tackling has never been that strong and he seems to have been bought to play out wide. And we need a completely different skill set out wide and circulating possession in a position where we need attacking thrust from is not sufficient and so if people criticise him for playing the safe pass and keeping the ball it is because more is expected from the position he plays in.
I highly doubt he is being groomed to play Lucas' role but it doesn't mean that they don't share certain attributes that make them similar. Like some others have said, I think he'll eventually be a central midfielder (though I can see certain reasons why he's being played out wide) and that's where players with him and Lucas' ability to retain possession and keep the ball moving is best utilised. The more players we have like the better, it'll allow us to consistently get more of a grip on the game than we have done and it'll give our front players more opportunities.
Your argument about him playing out wide I can see but bear in mind that that's not what some people are saying, they're saying he's a shithouse, they don't know what he does, he hides, he's not good enough etc as opposed to saying what he's not particularly suited out wide. If he has to play there, then you're right, though he has a lot of energy, he's not traditionally going to being a winger but we can do things to help him - our midfield is quite slow in moving the ball and if we can speed that up and find him early and in space, he does have the ability to put a cross in (better than most other players in our team) but also link up with his team mates but yeah, there are some problems with him being on the right - namely he not going to do what Downing (or at least what he was bought to do) or Suarez do and take people on and drive at people. Still, that's a completely different thing in comparison with what his critics are saying.