I didn't wantch him much except in two matches against Napoli.
His running was on Arda/Rakitic level, maybe even worse.
Seri is good when he needs to receive the ball and pass it forward, but other than that, he is weak in defending, somewhat slow, lacks stamina, doesn't run in counters (stays back to save the energy).
More or less, imagine a 40 years old Xavi. Good technique, passing, vision, zero pace, stamina, strength, defending.
Imo, people are over and over blinded by pure technical skills (Bernardo Silva also).
We need to move away from Barca from 10 years ago and with technical skills buy players with at least some basic minimum in physical skills (pace, stamina, strength).
Sadly, Seri doesn't even posses a bare minimum of those.
About the last season, you always need to be cautious. He could be a next Mahrez with one good season plus Ligue1 is quite average and teams don't press too much, so they have a slower style of play where midfielders have more time to think and pass easily (than in England and Spain). Also, a player who runs less can defensively survive more easily in that kind of a league.