If you have a monopoly over a platform, what is there to keep you from being lazy? Plenty of rich lazy fools spend lavishly, it wouldn't be an original story.
The size of a team working on one product at a large company has nothing to do with the size of the company or its real estate budget.
Sure, they could put more people on any particular project, if they thought it was important. But that's not necessarily going to make a UI decision any better.
Nobody outside Apple is likely to know how these decisions were made. We just see the results.
Whether it was the choice of an individual engineer or designer, or the choice of a high-level executive to not put anyone who cared about design on the Books team, the fact remains that Apple chose not to keep this animation.
You can blame companies for making bad decisions -- you can even describe them as "lazy" -- even if you don't know the exact details of the process the company uses to make bad decisions.
It's not a question of laziness it's a question of prioritization and opportunity cost.
The logical conclusion of your argument is Apple has lots of money therefore they should have finished everything already.
The small team assigned to port Books to iOS16 probably decided that spending a lot of effort porting the one animation is not worth the opportunity cost that could be spent on literally anything else.
I don't think it's what happened in this case, but extremely lazy crap makes it all the way to public releases for all the tech giants. Engineer count and cash-on-hand don't seem to have much to do with it.
1 https://www.apple.com/newsroom/2020/06/apple-reveals-lineup-...
2 https://www.weetas.com/article/apple-spaceship/