Emery was sacked rightfully for the dreadful run of form at the end of his tenure here, Arteta wasn't. How can the fact "he's still in the job" be an argument then, if it were you would have had to say Emery shouldn't have been fired until the day before he got the sack.
I think the Maguire talk was just papers linking us wasn' it? The guys Emery himself confirmed for wanting to buy were Fabinho Nkunku and Zaha, the latter doesn't have the highest ceiling but would've been a solid choice if he had been available for a reasonable fee, the other two obviously would've been massive buys for us. Maguire would've tarnished all other decisions of course but I haven't seen anything concrete
Anyway Emery won a European trophy which we never got and got to the CL Ro16 with a team that has no business being there really. I'd put good money on Arteta never in his life coaching a team just in the group stages.