Never heard of perez but 17 goals in la liga last season is nothing to be sniffed at
https://en.wikipedia.org/wiki/Lucas_Pérez
Honestly I'd say looking at a round up of his goals initial impression is someone who chases lost causes which gets him a few extra goals, works hard, is pretty fast/determined but scored a lot of fairly easy goals and several were monumental screw ups by defence/keeper.
Problem is in a decade that's his single good season. Giroud had 2 'good' seasons, both in a weak league but one of them in the second division as well. Welbeck, no great seasons, Gervinho, not sure he had anything great before he joined, I think he had one great season for Roma before they stopped playing him as much iirc.
Strikers who have one epic season with 2-3 times their more consistent rate are frankly a dime a dozen, those who are consistent are rare as hell. 17 goals isn't particularly huge for La Liga either. Gervinho, Chamakh, Welbeck, Giroud, Sanogo, Chu-Young, how many obviously not good enough strikers can Wenger buy but think he's somehow doing right by the club by not just spending more on a single great striker?
Honestly the only two semi worth strikers we've bought since RVP is Eduardo and Pod, the latter had really really impressive numbers with us but just wasn't used often enough then frozen out in the third season. Eduardo was insane up to his injury and then was pushed all over the place and used so sporadically he couldn't get back into his game. Wenger basically screwed around with him till he pushed him out.
Wenger needs to buy a top striker, put up with difficult personalities, stop getting rid of top players who you just don't like, stop buying insanely average strikers because they are cheap and actually try to win the damn league.