I always liked Rosicky as well to be fair, think his biggest problem was staying in one piece rather than lacking quality.
In Wenger's defence he has at least tried to add some steel to his midfield recently, after wilfully neglecting any defensive midfield presence for years, but they've just not worked out. I've liked what I've seen of Elneny the few times I've seen him but he's nothing spectacular, Xhaka came with a big reputation and even bigger pricetag but I've seen nothing of him either at Arsenal or before that suggest he's worth anything like that and he's an red card waiting to happen most weeks to boot.
Think they've sort of lost their way in recent years, they're still a side built on attacking/aesthetic principles but some of their signings/selections recently seem at odds with one another. At the end with RVP they had that freakish connection between him and Song, think there was a impressive amount of assists for the former by the latter in the one season with lofted balls for him to latch onto with space in behind. Then they got Giroud and ended up playing off him a lot more with midfielders bouncing stuff of him and running on for the returns, I was a big fan of this approach and seemed to bring out the best in the likes of Ramsey and Wilshere. Then that little link up went out the window with the signing of golden boy Ozil, who I don't think suits that approach very well at all, he seems to much prefer playing behind a pacier forward who he can play in behind rather than looking to interchange passes with someone to get in on goal himself. I think that's what's lead to Sanchez being used more centrally a lot more often this season, he works as a better outlet for what Ozil wants to do but then that compromises someone like Ramsey who is a bit too cavalier to play deeper in midfield without a proper defensive guy next to him or he gets shoved out wide which is a complete waste.
I think they've perhaps been a bit slapdash in that they've seen a big name available now they've got money to throw around and got them without really thinking about how they fit in too much, certainly with Ozil though Sanchez has largely worked well whether out wide or up top.