I agree Ayton ain't Poeltl, but I also think he's much better defensively than the numbers suggest. They also seem to think that he won't further improve his game. A starting five of
Murray/Vassell/Keldon/J. Collins/Ayton
has not only no defensive holes (with Keldon being the only neutral defender), but this are also 5 players who can all give you 20 points per game and the oldest of them is DJ being 25. People need to think how good that line up might be 3 years down the line when everybody enters their prime, especially in a weak west where most of the star players are on the wrong side of 30.
The bench would most likely be
Jones/Branham/Primo/Sochan/Z. Collins with 3 players on rookie deals which saves a lot of cap space.
Moving Poeltl, J-Rich, Langford and McDermott would free up another 40 million. Paying Keldon won't be a problem. Vassell's and DJ's extensions won't kick in until 2024. At that point Ayton and John Collins would have 2 years left on their contracts, so moving any of them in the future shouldn't be an issue either.
With 2 years left on DJ's contract right now it makes sense for the Spurs to take on these deals and become more top heavy.