Hmmm...I think that is debateable. We most definitely have the weakest keepers and defence in comparison to our rivals.
Midfield wise I think we are lacking a bit too...though I do have high hopes for Torreira and Guendozi.
Our attacking options are admittedly pretty decent as you rightly pointed out, but we don't have a star in our forward line like say Liverpool do in Salah, the Spuds in Kane or City in Aguero.
Our bench options outside of the attacking positions are very questionable too.
I do agree that coaching can and will likely improve some of these guys..but I also feel that Emery has inherited a very "Wenger" centric team and as such will want to make his own relative personnel changes.
I think Emery will build a decent team / squad in time so not all is lost.