Shanahan's offense can be very complicated and it does take some time to learn and mesh all the skill players. If you have a smart QB, who can make quick reads and throw accurately to a spot, this offense can churn like butter. Brock Purdy is a perfect example. Average arm, average athleticism, smallish, but he reads and releases to a spot very well.
That all said, I really expect that Lester is going to simplify the packages, game plans, and play-calling the first few weeks. Scripted plays at the beginning, and several highly rehearsed shot plays in the middle of the game, but beyond that, a lot of base offense.
I am excited to see how he folds in hybrid WRs like Wetgen in gadget and package plays. There is enough speed and talent to draw from for Lester to get creative with some reverses and screens to some of the smaller guys with wheels