I don't know where this narrative has come from that he'd only had a couple of bad seasons. His last two seasons were actually a little better than the few that came before them. He'd been declining ever since the 2018 World Cup. 17/18 was probably his best ever season, but his terrible World Cup that year seemed to destroy him mentally or something and he was never remotely the same after that. So his decline had been going for 5 years before he left which is more than just a bad patch.
18/19 he was ok for most of the season, where it wasn't a huge issue but he was obviously nowhere near his previous level. He was then atrocious for the last couple of months of that season, comfortably the worst form of his career where he was directly at fault for something like 8 goals in 12 games (and a few others he could have done better for).
19/20 he was shaky all season, including being at fault for three of the goals that got us knocked out of the League Cup and Europa League semi's.
20/21 he was so poor all season that even Ole (who was loyal to a fault to him) ended up dropping him for Henderson for the final few months of the season.
21/22 he was actually back to something like his best for the first half of the season, but he rapidly dropped off and was poor again in the second half.
22/23 was ok for most of the season, but once again he finished the season poorly (which was becoming a real trend).