I don't know which player you have been watching but Benteke is not very limited, your description is rather generic and your comparison to Fellaini is infact lazy for someone who has "seen him play numerous times".... Yes, he is an aerial threat, yes, he is really physical, those are qualities you can tell just by looking at the guy, and those are the only things people mostly say about him, he isn't limited, people that haven't seen much of him just place him in that particular category... and you should know this since you have watched Villa on numerous occasions.
Benteke is a really skilful player, he knows how to dribble - infact he is sometimes seen in the midfield trying to beat multiple players, sometimes he is successful and other times he gets dispossessed - which is one of his flaws - he holds on to the ball a little too much, which isn't a skill you necessarily want a striker to have although he does tend to draw in defenders giving other players(ideally the ones with pace) enough room to get into the box unmarked. He is very unpredictable, he can shoot the ball from outside the box with great accuracy, he can take on the last defender and beat him, he can dance around defenders and get the ball into the net even as he is being marked(see Evans,Hangeland), he is one of the few players in the league who is great at flick ons , he is also really good at key passes in the final 3rd, set pieces - and I'm not just talking about being at the end of one, and build up play - meaning he would thrive in a team that plays possession football.
I dont think i need to talk about his awareness in the box,physical presence,finishing and speed, and in regards to the lumping the ball into the box comment, i think anyone who has seen Aston Villa play would know that unlike Stoke and United, Villa aren't exactly that kind of team, they obviously play to his strengths (in this case aerial ability), but reducing their whole attack to just lumping the ball to Benteke is yet another lazy attempt at criticising Benteke.
"too slow to be a runner", "has poor control to be a target man" - stop it, I'm sorry but you are making stuff up at this point, your criticisms dont even seem logical, i mean its not like he has ADM,Mata,Herrera and co behind him, this is a striker for Aston Villa we're talking about, where does a slow striker with poor control go about scoring 10+ goals in the EPL without the services of top players ?
You think he is average? fine, but you have to (at the very least) be able to back it up with facts and not fiction, a striker that has proven himself in the EPL should definitely be in our shortlist.... he is just 24 years old and he still has room for improvement - just like every other player on the planet.