Wemby might well be ready to be a championship centrepiece earlier in his career than others were who won in year 7/8 of their careers. I know we crushed the Cavs in 07, but if LeBron had a better cast I think he was ready in year 4 - that, to me is the comparison point.
LeBron is an outlier success, and in terms of impact, probably is the closest to Wemby as a young rookie (Wemby's better, though older as a rookie, close enough) with a dominant path. If the Cavs did a better job building up the roster they might have been good enough to win if they got a break their way in the finals.
I think the Spurs should be thinking that Wemby is on that type of path, rather than a ready in year 8 path. I still think it's worth patience to build slowly (ish) with year 4 in mind, rather than thinking he's ready now. As good as he is, there are things to work on (Timing of taking early shots off the dribble, physical strength and ability to post up (see Holiday in the Denver game ), screen angles and slipping to take advantage of switches). Those little things will magnify his impact, move him up the total impact boards and make him a more championship ready piece as he'll have fewer holes to attack.
Slowly doesn't mean nothing, and if something comes up that means the Spurs can get an All NBA caliber player who fits, it's worth it to get the Shaq to Wemby's Wade. I don't see that as a realistic option - Curry, Luka, Shai, Hali, Brunson ain't moving, Mitc might in FA (seems dumb to trade for him at his asset value, perfectly fine swinging on him as a FA target), then you get into more fringe guys who aren't at that all NBA level (to me, Trae isn't an All-NBA level player), where trading for them is more about an asset play than truly opening up a championship window.