he was solidly average last year and is projected to be this year. he was really bad at 24 in 2019 and was bad for 36 games in 2020. is it not possible he’s improved? projection systems have the info you posted as well, and while they’re far from perfect, i trust them more than someone just adding up WAR.
I'm not high on the projection systems for him in terms of WAR. They all rate him as a good defender and that's not the case anymore. His defense has steadily eroded to the point that it's now below average. All of the projections project a wRC+ under 100 (some well under). If his defense doesn't miraculously improve, he's not going to sniff the WAR projections.
As for last year, his offensive numbers were aided by the way he was used. As a backup he was used situationally and, believe it or not, Snit seemed to do pretty well picking his matchups. But we got a glimpse of Arcia as a starter last year. When Ozzie went down in mid-June, Arcia stepped in. Arcia had appeared in one game in June before Ozzie got hurt so the vast majority of his June stats were as a starter and he started the vast majority of July. After that he went back to the bench with Grissom getting most of the playing time. So Arcia's June and July stats should show what he can do as a starter.
Over June and July, Arcia had 120 PAs. In June he posted a wOBA of .289 and a wRC+ of 82. In July his wOBA was .260 with a red hot wRC+ of 62.
We have a 120 PA snapshot of Arcia as a starter last year and the results are UGLY. People want to assume Arcia's WAR would increase at the same rate you increase his playing time but that's not a guarantee. You can't shield a player's weaknesses from being exposed when they're a starter. Sometimes the additional playing time drops a player's value like a rock.
I don't see anything in his stats to make me believe he's a 1.5 to 2 WAR player or that he's even average. We have 1,000 PAs over the last 4 years with a combined WAR of 0.1. In 2019 his WAR -0.9, in 2020 it was 0.7, in 2021 it was -0.4, last year it was 0.7. He's consistently within 1 WAR of 0. I see no reason to believe his 0.7 WAR last year is an indication he's improved as a player. It's well within what he's established as his standard range.