Issue is, you currently on paper have a better squad than we did last season and we finished 4th. Not saying Arteta has to do that or its failure, but you have a set starting Xl that should be atleast finishing top 7 if the majority of them are used most weeks. Furthermore, if Arteta decided to say "feck it I'll play what I (apparently) want to play, drill the system into my players and take the growing pains that will come until I have a Xl I want" like Klopp did would your results have been much worse than they have been (especially recently)? You may not have had the FA Cup but I'd wager you'd be a lot closer to where you ultimately want to be than you currently are and as fans you would be having a lot more fun on the way.
Also he doesn't really have to play a lot of the deadwood, as I shown with that lineup above, even without Partey you can bring out a lineup without playing Xhaka. He could also play AMN instead of Bellerin, he didn't have to sign Cedric and Mari, give Willian three years or offer Mustafi and Elnenny new deals (those two along with Xhaka were pretty much exilled until Arteta turned up and brought them back into the fold).
Would you say our squad was more complete than yours last season? I suppose that's a matter of opinion, not sure i necessarily agree with it mind you player for player, but there's no doubt we should be doing better, & Lampard did well with what he had. Just after the Utd game, think we were 4th in the table in terms or results since he joined, so he was doing ok. There's no doubt we've had a shocking month since though.
There's certainly a couple of different ways to approach it, not sure you can definitively say what's the right way. On paper, you think trying to give a team as lost as what Arsenal were some structure & tighten up the defence doesn't seem a silly thing to do, trying to cover weaknesses in midfield & defence seem sensible as well. Certainly no-one envisaged how bad the past month would be, so in hindsight perhaps he was wrong.
The signings of Cedric & Mari were low cost options to fill specific roles in the squad. He wanted a left footed centre back, & a specific right back as cover, especially because it was believed Maitland-Niles didn't want to play full back & would look to move in the summer. I'm not sure I believe the stories about Mustafi being offered a new deal, & Elneny has been our best midfielder this season overall (that tells a story in itself) & is a useful squad player.
The signing of Willian hasn't worked out, that's for sure. That's 1 I certainly don't think we needed for sure, certainly in this form anyway! :-)