That's not necessarily true — him and Isak were playing quite well together at Real Sociedad.
@Osman will attest to this. Real just don't have room for him, same thing as Hakimi or Theo Hernández
Yeah besides first eredivisie loan spell with Hereeneven, he has been fantastic impact player off the bat with Vitesse and Real Sociedad. Regularly winning player of the month awards, and being one of the first names in team of the year.
He was easily the best la liga player outside the classico teams. He plays more direct a bit and scoring uptick with Arsenal, but that's because they have score by committee team style instead of feed one guy.
He is just all around fantastic key midfielder and has been for years.
No shame in not having space to shine in 4 times out of 5 CL winners with Modric and Kroos ahead of him.
Also Arteta uses him smart, most thought you must only play him as central AM nr 10, a dying breed role in todays game, but Arteta gives him a mixed of a nr 10 and a nr 8 drifting to the right, allowing him to become less predictable and more lethal with his left from that position.