Very solid is a bit of an overstatement mate. For passing, he had the lowest passes out of anyone in the backline - Dav passed more than he did. For defensive stats, Reggie blows him out of the water - 5 tackles, 5 interceptions and 2 clearances to Doherty's 1, 4 and 1 respectively - exactly double the numbers, without any fouls for Reggie versus two given away by Doherty. And the yellow card for Doherty as well.
Same thing attacking-wise - Reggie did a far better job, and
@SteveAWOL 's map of actions shows the sheer number and variety of Reguilon's crosses and attacking actions versus basically nothing from Doherty into the box.
And, as I've mentioned, he got beaten to the ball about thrice in the game, left space in behind twice, got left for dead twice. None of that will show in the stats, but it will be evident in game.
Reggie is lightyears ahead of Doherty, and the comparison makes it even worse for Doc - the guy is supposed to be an experienced Premier League full- back, but is being left for dead both by Aurier this season and Reggie on the other flank, a raw kid fresh from La Liga.
Only one of our fullbacks as mediocre-to-poor as Doherty has been this season is Davies.
I'm giving him a chance next season because he had COVID and it might be tough settling in. But I'm done with him for this season, and Japhet should start every game Aurier's not fit for. If we're playing that wonky system again as you say, even better - Tanganga's a centre-back by training, he'd do a better job than Doherty at that, easy.