In Arteta's credit aswell he won the FA Cup final in his first season. I just looked it up and they beat Chelsea that year, who were the league winners (Conte right? who had a bloody good side)
In regards to Poch though, he amounted a similar title challenge with Spuds, maintained CL positioning for a number of seasons and reached a CL final. So he already has shown more pedigree than Arteta. This all ignoring PSG stint for the obvious reason of it being a one team league.
We will see what he can do with Chelsea. There signing policy has not been kind to him in fairness. Alot of potential but little realities, and those close to reality had long term injuries.
ETH yeah, needs to do much better next season. Let's see if their new board, and sporting direction can help him build a better squad. Just like Xavi, keep him out of the transfer decision making.
Poch has been on a downfall for years though. CL final is quite some time ago, back in 2019. At PSG he was pretty average, and his league position these days is simply unacceptable.
The manager also adds plus-value to the team. The squads of United and Chelsea are very good. Not elite like City of course, but far better than their current results would suggest. United for example had a piss easy CL group this season, should have easily ended up 2nd, and ETH managed to end up 4th. Against 3rd level teams like Galatasaray and Coppenhagen no less.
They have done a mediocre job at best so far. What will happen over the next seasons we shall see, that is if they still get credit to prove themselves and don't get sacked in the process.
Nobody expects them to challenge for the title so early, but they of course have to do much better than they did so far. Should be involved in the battle for the 4th position, not so many points behind Villa/Tottenham.