I'd go even further and break down the Brown/Tatum era even more.
'16-'18 (includes 1 year pre-Tatum): this feels like an A to A+. One of the best times to be a hardcore fan like most of us are. Got to root for the team to succeed in the present (2 ECF appearances) while also being able to follow the draft with high level lotto picks, as well as the free agent market with cap room and trade market with a war chest of assets. Nailed the most important draft picks, went 2 for 3 on big name free agents, team was constantly improving without tanking. This was awesome. Major misses being Durant, not dethroning LeBron in '18, Hayward's injury, and some would argue not making an all-in trade for Kawhi/Butler/Davis/George.
'19-'21: D+ to C-. Blew a great opportunity in '19 with team issues. Was able to tread water bringing in Kemba, but still had more talent going out than coming back in (losing Kyrie, Horford, Rozier, Hayward, Morris, while bringing in Kemba, Teague, Fournier, Kanter, Richardson, Schroder). No big moves. Still had some late lotto picks to root for, but no major draft success (not to say there weren't some solid hits though). Blew an opportunity in the bubble with another Hayward injury. This was a disappointing part of the era, but still came within spitting distance of the Finals. Ended with Danny leaving, Stevens stepping away from the bench, personally wasn't seeing any championship success on the horizon.
'22-'24: A. Was not expecting a championship contender going into '22 and current day juggernaut we have now, but here we are. Team made several big moves (Horford, White, Brogdon/Holiday, Porzingis) where every trade seems like a hit. '23 was disappointing, and the team could be looking at 3 Finals, 2-3 championships, but best team can get now is 1 ring. 2 Finals and hopefully 1 ring, still pretty good though.
Overall I'd say A, which seems generous given how long I rank that '19-'21 mini-era, but the years around it, and present day success/outlook make up for it.