Kingery played centerfield in college (not forever obviously), and what good would it even do for the Phillies to try and make him a full-time 2B now? They still have Segura next year and there's also a non-zero chance Didi moves from SS if they Phillies hit that free agent market.
Obviously the Phillies are not the Rays or Dodgers and Kingery is not Chris Taylor or Ben Zobrist, which is too bad for both the team and the player, but if he doesn't win the CF job he's the utility infielder, and still probably better than Maton or Chatham. He's certainly not going to go to the alternate site, maybe if he's still terrible in May they could consider AAA.
I'm sure there's some truth to the notion that the position-switching affects his offense, it is just more stuff to think about - which glove, positioning, tracking the ball off the bat - but it's not the reason for his struggles (and right now, while he obviously still has a long way to go to get back to where he was in the first half of 2019, I think it's just the hangover from COVID and the injuries).
And when is the last time the Phillies successfully demoted an established but struggling young position player to get him back on track? Every guy I can think of - Brown, Asche, Nick Williams, Franco - it meant the end of their career.
And every team has a guy on their roster who can't play "batter." You just don't usually pay Phil Gosselin or Wilson Valdez $4 million.