Jack Harrison's best happened on the left under Marcelo Bielsa, and the peak was their promotion year in 20/21, the last year that he was partnered with Ezgjan Alioski at LB. They'd had a lot of success together in the Championship, but Alioski departed for Saudi money following the promotion year. Harrison had 8 goals and 8 assists that season.
The following year, without Alioski, Harrison had a barren first half, but eventually settled into a partnership with Luke Ayling. In the second hald, he scored a winner against Dyche's Burnley and then a hat trick against Moyes's West Ham, finishing 8 goals and an assist on the year.
In his last year at Leeds, he played all over the pitch, and managed 3 goals and 5 assists from the left in just 13 games, 2 and 2 from the right in 12, and nothing from the middle in 7.
It seems clear that Harrison was most effective from the left, and especially while working with an attacking fullback, which he had in both Alioski and Ayling. He's never done anything as a 10.
After moving to Everton, he was completely exposed, playing almost entirely on the right, and pretty much in isolation with no one running in behind. He played 21 times on the right this year and came out with one assist. By contrast, his lone goals came from one of just a handful of appearances on the left.
In short, don't be too harsh on Jack Harrison. He was never made to play in isolation as a right winger, but the club had no options and needed him to play there. There was no depth, no competition — just players plugged in where needed. In the best case scenario, he'd have played the odd game or come on as a substitute on the left to bring in fresh legs and a late scoring threat. He'd have been more effective, especially if used to his strengths, but it's not like he gave up on the team or didn't try.
